diff --git a/packages/bulk-edit/src/browser/bulk-edit-tree/bulk-edit-node-selection.ts b/packages/bulk-edit/src/browser/bulk-edit-tree/bulk-edit-node-selection.ts
index 179018ceacd42..4ff9f01ddaac5 100644
--- a/packages/bulk-edit/src/browser/bulk-edit-tree/bulk-edit-node-selection.ts
+++ b/packages/bulk-edit/src/browser/bulk-edit-tree/bulk-edit-node-selection.ts
@@ -17,13 +17,14 @@
 import { SelectionService } from '@theia/core/lib/common/selection-service';
 import { SelectionCommandHandler } from '@theia/core/lib/common/selection-command-handler';
 import { ResourceFileEdit, ResourceTextEdit } from '@theia/monaco-editor-core/esm/vs/editor/browser/services/bulkEditService';
+import { Is } from '@theia/core/lib/common/is';
 
 export interface BulkEditNodeSelection {
     bulkEdit: ResourceFileEdit | ResourceTextEdit;
 }
 export namespace BulkEditNodeSelection {
     export function is(arg: unknown): arg is BulkEditNodeSelection {
-        return !!arg && typeof arg === 'object' && ('bulkEdit' in arg);
+        return Is.object(arg) && 'bulkEdit' in arg;
     }
 
     export class CommandHandler extends SelectionCommandHandler<BulkEditNodeSelection> {
diff --git a/packages/core/shared/reflect-metadata/index.d.ts b/packages/core/shared/reflect-metadata/index.d.ts
new file mode 100644
index 0000000000000..7b873b4cc900a
--- /dev/null
+++ b/packages/core/shared/reflect-metadata/index.d.ts
@@ -0,0 +1 @@
+export * from 'reflect-metadata';
diff --git a/packages/core/shared/reflect-metadata/index.js b/packages/core/shared/reflect-metadata/index.js
new file mode 100644
index 0000000000000..2184c277f4f1a
--- /dev/null
+++ b/packages/core/shared/reflect-metadata/index.js
@@ -0,0 +1 @@
+module.exports = require('reflect-metadata');
diff --git a/packages/core/src/browser/frontend-application.ts b/packages/core/src/browser/frontend-application.ts
index 3be0d1f878139..b07809eb03307 100644
--- a/packages/core/src/browser/frontend-application.ts
+++ b/packages/core/src/browser/frontend-application.ts
@@ -15,7 +15,7 @@
 // *****************************************************************************
 
 import { inject, injectable, named } from 'inversify';
-import { ContributionProvider, CommandRegistry, MenuModelRegistry, isOSX, BackendStopwatch, LogLevel, Stopwatch } from '../common';
+import { ContributionProvider, CommandRegistry, MenuModelRegistry, isOSX, BackendStopwatch, LogLevel, Stopwatch, Is } from '../common';
 import { MaybePromise } from '../common/types';
 import { KeybindingRegistry } from './keybinding';
 import { Widget } from './widgets';
@@ -101,7 +101,7 @@ export interface OnWillStopAction<T = unknown> {
 
 export namespace OnWillStopAction {
     export function is(candidate: unknown): candidate is OnWillStopAction {
-        return typeof candidate === 'object' && !!candidate && 'action' in candidate && 'reason' in candidate;
+        return Is.object(candidate) && 'action' in candidate && 'reason' in candidate;
     }
 }
 
diff --git a/packages/core/src/browser/label-parser.ts b/packages/core/src/browser/label-parser.ts
index 3aa4dec730ae6..7b8a75724804b 100644
--- a/packages/core/src/browser/label-parser.ts
+++ b/packages/core/src/browser/label-parser.ts
@@ -14,6 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 import { injectable } from 'inversify';
+import { Is } from '../common/is';
 
 export interface LabelIcon {
     name: string;
@@ -21,8 +22,8 @@ export interface LabelIcon {
 }
 
 export namespace LabelIcon {
-    export function is(val: object): val is LabelIcon {
-        return 'name' in val;
+    export function is(val: unknown): val is LabelIcon {
+        return Is.object<LabelIcon>(val) && Is.string(val.name);
     }
 }
 
diff --git a/packages/core/src/browser/label-provider.ts b/packages/core/src/browser/label-provider.ts
index 48e61a057efb3..80bda25d51fbb 100644
--- a/packages/core/src/browser/label-provider.ts
+++ b/packages/core/src/browser/label-provider.ts
@@ -19,7 +19,7 @@ import * as fileIcons from 'file-icons-js';
 import URI from '../common/uri';
 import { ContributionProvider } from '../common/contribution-provider';
 import { Prioritizeable } from '../common/types';
-import { Event, Emitter, Disposable, Path } from '../common';
+import { Event, Emitter, Disposable, Path, Is } from '../common';
 import { FrontendApplicationContribution } from './frontend-application';
 import { EnvVariablesServer } from '../common/env-variables/env-variables-protocol';
 import { ResourceLabelFormatter, ResourceLabelFormatting } from '../common/label-protocol';
@@ -99,7 +99,7 @@ export interface URIIconReference {
 }
 export namespace URIIconReference {
     export function is(element: unknown): element is URIIconReference {
-        return !!element && typeof element === 'object' && 'kind' in element && (element as URIIconReference).kind === 'uriIconReference';
+        return Is.object(element) && element.kind === 'uriIconReference';
     }
     export function create(id: URIIconReference['id'], uri?: URI): URIIconReference {
         return { kind: 'uriIconReference', id, uri };
diff --git a/packages/core/src/browser/navigatable-types.ts b/packages/core/src/browser/navigatable-types.ts
index a52f39491d139..0ba350585121a 100644
--- a/packages/core/src/browser/navigatable-types.ts
+++ b/packages/core/src/browser/navigatable-types.ts
@@ -17,6 +17,7 @@
 import URI from '../common/uri';
 import { MaybeArray } from '../common/types';
 import { Widget, BaseWidget } from './widgets';
+import { Is } from '../common/is';
 
 /**
  * `Navigatable` provides an access to an URI of an underlying instance of `Resource`.
@@ -34,7 +35,7 @@ export interface Navigatable {
 
 export namespace Navigatable {
     export function is(arg: unknown): arg is Navigatable {
-        return !!arg && typeof arg === 'object' && 'getResourceUri' in arg && 'createMoveToUri' in arg;
+        return Is.object(arg) && 'getResourceUri' in arg && 'createMoveToUri' in arg;
     }
 }
 
@@ -71,12 +72,12 @@ export namespace NavigatableWidget {
 }
 
 export interface NavigatableWidgetOptions {
-    kind: 'navigatable',
-    uri: string,
-    counter?: number,
+    kind: 'navigatable';
+    uri: string;
+    counter?: number;
 }
 export namespace NavigatableWidgetOptions {
     export function is(arg: unknown): arg is NavigatableWidgetOptions {
-        return !!arg && typeof arg === 'object' && 'kind' in arg && (arg as NavigatableWidgetOptions).kind === 'navigatable';
+        return Is.object(arg) && arg.kind === 'navigatable';
     }
 }
diff --git a/packages/core/src/browser/preferences/injectable-preference-proxy.ts b/packages/core/src/browser/preferences/injectable-preference-proxy.ts
index b5addbf63c613..49c4afa002db8 100644
--- a/packages/core/src/browser/preferences/injectable-preference-proxy.ts
+++ b/packages/core/src/browser/preferences/injectable-preference-proxy.ts
@@ -16,7 +16,7 @@
 
 import { inject, injectable, postConstruct } from 'inversify';
 import { PreferenceSchema } from '../../common/preferences/preference-schema';
-import { Disposable, DisposableCollection, Emitter, Event, MaybePromise } from '../../common';
+import { Disposable, DisposableCollection, Emitter, Event, Is, MaybePromise } from '../../common';
 import { PreferenceChangeEvent, PreferenceEventEmitter, PreferenceProxy, PreferenceProxyOptions, PreferenceRetrieval } from './preference-proxy';
 import { PreferenceChange, PreferenceChangeImpl, PreferenceChanges, PreferenceScope, PreferenceService } from './preference-service';
 import { JSONValue } from '@phosphor/coreutils';
@@ -103,7 +103,9 @@ export class InjectablePreferenceProxy<T extends Record<string, JSONValue>> impl
     }
 
     get(target: unknown, property: string, receiver: unknown): unknown {
-        if (typeof property !== 'string') { throw new Error(`Unexpected property: ${String(property)}`); }
+        if (typeof property !== 'string') {
+            throw new Error(`Unexpected property: ${String(property)}`);
+        }
         const preferenceName = this.prefix + property;
         if (this.schema && (this.isFlat || !property.includes('.')) && this.schema.properties[preferenceName]) {
             const { overrideIdentifier } = this;
@@ -143,7 +145,7 @@ export class InjectablePreferenceProxy<T extends Record<string, JSONValue>> impl
             } while (parentSegment && value === undefined);
 
             let segment;
-            while (typeof value === 'object' && (segment = segments.pop())) {
+            while (Is.object(value) && (segment = segments.pop())) {
                 value = value[segment];
             }
             return segments.length ? undefined : value;
diff --git a/packages/core/src/browser/preferences/preference-contribution.ts b/packages/core/src/browser/preferences/preference-contribution.ts
index 568baa849d1f5..6cf16349997e0 100644
--- a/packages/core/src/browser/preferences/preference-contribution.ts
+++ b/packages/core/src/browser/preferences/preference-contribution.ts
@@ -16,7 +16,7 @@
 
 import * as Ajv from 'ajv';
 import { inject, injectable, interfaces, named, postConstruct } from 'inversify';
-import { ContributionProvider, bindContributionProvider, Emitter, Event, Disposable } from '../../common';
+import { ContributionProvider, bindContributionProvider, Emitter, Event, Disposable, Is } from '../../common';
 import { PreferenceScope } from './preference-scope';
 import { PreferenceProvider, PreferenceProviderDataChange } from './preference-provider';
 import {
@@ -80,7 +80,7 @@ export interface FrontendApplicationPreferenceConfig extends FrontendApplication
 }
 export namespace FrontendApplicationPreferenceConfig {
     export function is(config: FrontendApplicationConfig): config is FrontendApplicationPreferenceConfig {
-        return 'preferences' in config && typeof config['preferences'] === 'object';
+        return Is.object(config.preferences);
     }
 }
 
diff --git a/packages/core/src/browser/preferences/preference-language-override-service.ts b/packages/core/src/browser/preferences/preference-language-override-service.ts
index 37a3cfddd1c58..aa2e346dc5697 100644
--- a/packages/core/src/browser/preferences/preference-language-override-service.ts
+++ b/packages/core/src/browser/preferences/preference-language-override-service.ts
@@ -15,7 +15,7 @@
 // *****************************************************************************
 
 import { injectable } from 'inversify';
-import { escapeRegExpCharacters } from '../../common';
+import { escapeRegExpCharacters, Is } from '../../common';
 import { PreferenceSchemaProperties } from '../../common/preferences/preference-schema';
 
 export interface OverridePreferenceName {
@@ -24,7 +24,7 @@ export interface OverridePreferenceName {
 }
 export namespace OverridePreferenceName {
     export function is(arg: unknown): arg is OverridePreferenceName {
-        return !!arg && typeof arg === 'object' && 'preferenceName' in arg && 'overrideIdentifier' in arg;
+        return Is.object(arg) && 'preferenceName' in arg && 'overrideIdentifier' in arg;
     }
 }
 
diff --git a/packages/core/src/browser/preferences/preference-provider.ts b/packages/core/src/browser/preferences/preference-provider.ts
index 256d5da180859..1b1bf43a134fd 100644
--- a/packages/core/src/browser/preferences/preference-provider.ts
+++ b/packages/core/src/browser/preferences/preference-provider.ts
@@ -20,7 +20,7 @@ import debounce = require('p-debounce');
 import { injectable, inject } from 'inversify';
 import { JSONExt, JSONValue } from '@phosphor/coreutils';
 import URI from '../../common/uri';
-import { Disposable, DisposableCollection, Emitter, Event } from '../../common';
+import { Disposable, DisposableCollection, Emitter, Event, Is } from '../../common';
 import { Deferred } from '../../common/promise-util';
 import { PreferenceScope } from './preference-scope';
 import { PreferenceLanguageOverrideService } from './preference-language-override-service';
@@ -253,16 +253,12 @@ export abstract class PreferenceProvider implements Disposable {
 
     protected getParsedContent(jsonData: any): { [key: string]: any } {
         const preferences: { [key: string]: any } = {};
-        if (typeof jsonData !== 'object') {
+        if (!Is.object(jsonData)) {
             return preferences;
         }
-        // eslint-disable-next-line guard-for-in
-        for (const preferenceName in jsonData) {
-            const preferenceValue = jsonData[preferenceName];
+        for (const [preferenceName, preferenceValue] of Object.entries(jsonData)) {
             if (this.preferenceOverrideService.testOverrideValue(preferenceName, preferenceValue)) {
-                // eslint-disable-next-line guard-for-in
-                for (const overriddenPreferenceName in preferenceValue) {
-                    const overriddenValue = preferenceValue[overriddenPreferenceName];
+                for (const [overriddenPreferenceName, overriddenValue] of Object.entries(preferenceValue)) {
                     preferences[`${preferenceName}.${overriddenPreferenceName}`] = overriddenValue;
                 }
             } else {
diff --git a/packages/core/src/browser/preferences/preference-proxy.ts b/packages/core/src/browser/preferences/preference-proxy.ts
index 7a266c9532311..efdf0831cce50 100644
--- a/packages/core/src/browser/preferences/preference-proxy.ts
+++ b/packages/core/src/browser/preferences/preference-proxy.ts
@@ -16,7 +16,7 @@
 
 /* eslint-disable @typescript-eslint/no-explicit-any */
 
-import { Disposable, Event, MaybePromise } from '../../common';
+import { Disposable, Event, Is, MaybePromise } from '../../common';
 import { PreferenceService } from './preference-service';
 import { PreferenceSchema } from './preference-contribution';
 import { PreferenceScope } from './preference-scope';
@@ -332,7 +332,7 @@ export function createPreferenceProxy<T>(preferences: PreferenceService, promise
             } while (parentSegment && value === undefined);
 
             let segment;
-            while (typeof value === 'object' && (segment = segments.pop())) {
+            while (Is.object(value) && (segment = segments.pop())) {
                 value = value[segment];
             }
             return segments.length ? undefined : value;
diff --git a/packages/core/src/browser/saveable.ts b/packages/core/src/browser/saveable.ts
index 06f5571c18140..c306bd32f75e4 100644
--- a/packages/core/src/browser/saveable.ts
+++ b/packages/core/src/browser/saveable.ts
@@ -22,6 +22,7 @@ import { Key } from './keyboard/keys';
 import { AbstractDialog } from './dialogs';
 import { waitForClosed } from './widgets';
 import { nls } from '../common/nls';
+import { Is } from '../common/is';
 
 export interface Saveable {
     readonly dirty: boolean;
@@ -60,10 +61,10 @@ export namespace Saveable {
 
     export type Snapshot = { value: string } | { read(): string | null };
     export function isSource(arg: unknown): arg is SaveableSource {
-        return typeof arg === 'object' && !!arg && is((arg as SaveableSource).saveable);
+        return Is.object<SaveableSource>(arg) && is(arg.saveable);
     }
     export function is(arg: unknown): arg is Saveable {
-        return typeof arg === 'object' && !!arg && 'dirty' in arg && 'onDirtyChanged' in arg;
+        return Is.object(arg) && 'dirty' in arg && 'onDirtyChanged' in arg;
     }
     export function get(arg: unknown): Saveable | undefined {
         if (is(arg)) {
diff --git a/packages/core/src/browser/shell/application-shell.ts b/packages/core/src/browser/shell/application-shell.ts
index 272a06bfde5f8..6c00418c2ce7d 100644
--- a/packages/core/src/browser/shell/application-shell.ts
+++ b/packages/core/src/browser/shell/application-shell.ts
@@ -22,7 +22,7 @@ import {
 } from '@phosphor/widgets';
 import { Message } from '@phosphor/messaging';
 import { IDragEvent } from '@phosphor/dragdrop';
-import { RecursivePartial, Event as CommonEvent, DisposableCollection, Disposable, environment } from '../../common';
+import { RecursivePartial, Event as CommonEvent, DisposableCollection, Disposable, environment, Is } from '../../common';
 import { animationFrame } from '../browser';
 import { Saveable, SaveableWidget, SaveOptions, SaveableSource } from '../saveable';
 import { StatusBarImpl, StatusBarEntry, StatusBarAlignment } from '../status-bar/status-bar';
@@ -2101,7 +2101,7 @@ export namespace ApplicationShell {
 
     export namespace TrackableWidgetProvider {
         export function is(widget: unknown): widget is TrackableWidgetProvider {
-            return !!widget && typeof widget === 'object' && 'getTrackableWidgets' in widget;
+            return Is.object(widget) && 'getTrackableWidgets' in widget;
         }
     }
 
diff --git a/packages/core/src/browser/shell/shell-layout-restorer.ts b/packages/core/src/browser/shell/shell-layout-restorer.ts
index ac7f680ff70fe..9e138923252c6 100644
--- a/packages/core/src/browser/shell/shell-layout-restorer.ts
+++ b/packages/core/src/browser/shell/shell-layout-restorer.ts
@@ -28,6 +28,7 @@ import { ApplicationShell, applicationShellLayoutVersion, ApplicationShellLayout
 import { CommonCommands } from '../common-frontend-contribution';
 import { WindowService } from '../window/window-service';
 import { StopReason } from '../../common/frontend-application-state';
+import { Is } from '../../common/is';
 
 /**
  * A contract for widgets that want to store and restore their inner state, between sessions.
@@ -47,7 +48,7 @@ export interface StatefulWidget {
 
 export namespace StatefulWidget {
     export function is(arg: unknown): arg is StatefulWidget {
-        return !!arg && typeof arg === 'object' && typeof (arg as StatefulWidget).storeState === 'function' && typeof (arg as StatefulWidget).restoreState === 'function';
+        return Is.object<StatefulWidget>(arg) && Is.func(arg.storeState) && Is.func(arg.restoreState);
     }
 }
 
@@ -232,11 +233,7 @@ export class ShellLayoutRestorer implements CommandContribution {
         const parseContext = new ShellLayoutRestorer.ParseContext();
         const layout = this.parse<ApplicationShell.LayoutData>(layoutData, parseContext);
 
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        let layoutVersion: number | any;
-        try {
-            layoutVersion = 'version' in layout && Number(layout.version);
-        } catch { /* no-op */ }
+        const layoutVersion = Number(layout.version);
         if (typeof layoutVersion !== 'number' || Number.isNaN(layoutVersion)) {
             throw new Error('could not resolve a layout version');
         }
@@ -282,9 +279,8 @@ export class ShellLayoutRestorer implements CommandContribution {
                     });
                 }
                 return widgets;
-            } else if (value && typeof value === 'object' && !Array.isArray(value)) {
-                // eslint-disable-next-line @typescript-eslint/no-explicit-any
-                const copy: any = {};
+            } else if (Is.object<Record<string, WidgetDescription>>(value) && !Array.isArray(value)) {
+                const copy: Record<string, unknown> = {};
                 for (const p in value) {
                     if (this.isWidgetProperty(p)) {
                         parseContext.push(async context => {
@@ -306,7 +302,7 @@ export class ShellLayoutRestorer implements CommandContribution {
                 // don't catch exceptions, if one migration fails all should fail.
                 const migrated = await migration.onWillInflateWidget(desc, context);
                 if (migrated) {
-                    if (migrated.innerWidgetState && typeof migrated.innerWidgetState !== 'string') {
+                    if (Is.object(migrated.innerWidgetState)) {
                         // in order to inflate nested widgets
                         migrated.innerWidgetState = JSON.stringify(migrated.innerWidgetState);
                     }
diff --git a/packages/core/src/browser/shell/tab-bar-toolbar/tab-bar-toolbar-types.ts b/packages/core/src/browser/shell/tab-bar-toolbar/tab-bar-toolbar-types.ts
index acf15dd917bbc..1e9f9a9b6010c 100644
--- a/packages/core/src/browser/shell/tab-bar-toolbar/tab-bar-toolbar-types.ts
+++ b/packages/core/src/browser/shell/tab-bar-toolbar/tab-bar-toolbar-types.ts
@@ -15,7 +15,7 @@
 // *****************************************************************************
 
 import * as React from 'react';
-import { ArrayUtils, Event, MenuPath } from '../../../common';
+import { ArrayUtils, Event, Is, MenuPath } from '../../../common';
 import { Widget } from '../../widgets';
 
 /** Items whose group is exactly 'navigation' will be rendered inline. */
@@ -27,13 +27,9 @@ export interface TabBarDelegator extends Widget {
 }
 
 export namespace TabBarDelegator {
-    export const is = (candidate?: Widget): candidate is TabBarDelegator => {
-        if (candidate) {
-            const asDelegator = candidate as TabBarDelegator;
-            return typeof asDelegator.getTabBarDelegate === 'function';
-        }
-        return false;
-    };
+    export function is(candidate?: Widget): candidate is TabBarDelegator {
+        return Is.object<TabBarDelegator>(candidate) && Is.func(candidate.getTabBarDelegate);
+    }
 }
 
 interface RegisteredToolbarItem {
@@ -172,14 +168,13 @@ export namespace TabBarToolbarItem {
     };
 
     export function is(arg: unknown): arg is TabBarToolbarItem {
-        return !!arg && typeof arg === 'object' && 'command' in arg && typeof (arg as TabBarToolbarItem).command === 'string';
+        return Is.object<TabBarToolbarItem>(arg) && Is.string(arg.command);
     }
 
 }
 
 export namespace MenuToolbarItem {
     export function getMenuPath(item: AnyToolbarItem): MenuPath | undefined {
-        const asDelegate = item as MenuToolbarItem;
-        return Array.isArray(asDelegate.menuPath) ? asDelegate.menuPath : undefined;
+        return Array.isArray(item.menuPath) ? item.menuPath : undefined;
     }
 }
diff --git a/packages/core/src/browser/shell/tab-bar-toolbar/tab-bar-toolbar.tsx b/packages/core/src/browser/shell/tab-bar-toolbar/tab-bar-toolbar.tsx
index 7776842ebf958..dc5a8975743c3 100644
--- a/packages/core/src/browser/shell/tab-bar-toolbar/tab-bar-toolbar.tsx
+++ b/packages/core/src/browser/shell/tab-bar-toolbar/tab-bar-toolbar.tsx
@@ -109,7 +109,7 @@ export class TabBarToolbar extends ReactWidget {
         const classNames = [];
         if (item.text) {
             for (const labelPart of this.labelParser.parse(item.text)) {
-                if (typeof labelPart !== 'string' && LabelIcon.is(labelPart)) {
+                if (LabelIcon.is(labelPart)) {
                     const className = `fa fa-${labelPart.name}${labelPart.animation ? ' fa-' + labelPart.animation : ''}`;
                     classNames.push(...className.split(' '));
                 } else {
diff --git a/packages/core/src/browser/source-tree/tree-source.ts b/packages/core/src/browser/source-tree/tree-source.ts
index e0dc628eeabe8..9251f5cd427e6 100644
--- a/packages/core/src/browser/source-tree/tree-source.ts
+++ b/packages/core/src/browser/source-tree/tree-source.ts
@@ -22,6 +22,7 @@ import { Emitter, Event } from '../../common/event';
 import { MaybePromise } from '../../common/types';
 import { Disposable, DisposableCollection } from '../../common/disposable';
 import { TreeWidget } from '../tree';
+import { Is } from '../../common/is';
 
 export interface TreeElement {
     /** default: parent id + position among siblings */
@@ -39,7 +40,7 @@ export interface CompositeTreeElement extends TreeElement {
 }
 export namespace CompositeTreeElement {
     export function is(element: unknown): element is CompositeTreeElement {
-        return !!element && typeof element === 'object' && 'getElements' in element;
+        return Is.object(element) && 'getElements' in element;
     }
     export function hasElements(element: unknown): element is CompositeTreeElement {
         return is(element) && element.hasElements !== false;
diff --git a/packages/core/src/browser/status-bar/status-bar.tsx b/packages/core/src/browser/status-bar/status-bar.tsx
index 4d24eb4a8e130..2400710d0fff3 100644
--- a/packages/core/src/browser/status-bar/status-bar.tsx
+++ b/packages/core/src/browser/status-bar/status-bar.tsx
@@ -161,7 +161,7 @@ export class StatusBarImpl extends ReactWidget implements StatusBar {
         const children: JSX.Element[] = [];
 
         childStrings.forEach((val, key) => {
-            if (!(typeof val === 'string') && LabelIcon.is(val)) {
+            if (LabelIcon.is(val)) {
                 const animation = val.animation ? ` fa-${val.animation}` : '';
                 if (val.name.startsWith('codicon-')) {
                     children.push(<span key={key} className={`codicon ${val.name}${animation}`}></span>);
diff --git a/packages/core/src/browser/tree/tree-selection.ts b/packages/core/src/browser/tree/tree-selection.ts
index d358008b91ba7..34cef93f3bb11 100644
--- a/packages/core/src/browser/tree/tree-selection.ts
+++ b/packages/core/src/browser/tree/tree-selection.ts
@@ -15,7 +15,7 @@
 // *****************************************************************************
 
 import { TreeNode } from './tree';
-import { Event, Disposable, SelectionProvider } from '../../common';
+import { Event, Disposable, SelectionProvider, Is } from '../../common';
 
 /**
  * The tree selection service.
@@ -87,7 +87,7 @@ export namespace TreeSelection {
     }
 
     export function is(arg: unknown): arg is TreeSelection {
-        return !!arg && typeof arg === 'object' && 'node' in arg;
+        return Is.object(arg) && 'node' in arg;
     }
 
     export function isRange(arg: TreeSelection | SelectionType | undefined): boolean {
diff --git a/packages/core/src/browser/tree/tree.ts b/packages/core/src/browser/tree/tree.ts
index 8a65875b61499..0ca750bec6730 100644
--- a/packages/core/src/browser/tree/tree.ts
+++ b/packages/core/src/browser/tree/tree.ts
@@ -20,6 +20,7 @@ import { Disposable, DisposableCollection } from '../../common/disposable';
 import { CancellationToken, CancellationTokenSource } from '../../common/cancellation';
 import { Mutable } from '../../common/types';
 import { timeout } from '../../common/promise-util';
+import { Is } from '../../common/is';
 
 export const Tree = Symbol('Tree');
 
@@ -124,7 +125,7 @@ export interface TreeNode {
 
 export namespace TreeNode {
     export function is(node: unknown): node is TreeNode {
-        return !!node && typeof node === 'object' && 'id' in node && 'parent' in node;
+        return Is.object(node) && 'id' in node && 'parent' in node;
     }
 
     export function equals(left: TreeNode | undefined, right: TreeNode | undefined): boolean {
@@ -148,7 +149,7 @@ export interface CompositeTreeNode extends TreeNode {
 
 export namespace CompositeTreeNode {
     export function is(node: unknown): node is CompositeTreeNode {
-        return typeof node === 'object' && !!node && 'children' in node;
+        return Is.object(node) && 'children' in node;
     }
 
     export function getFirstChild(parent: CompositeTreeNode): TreeNode | undefined {
diff --git a/packages/core/src/browser/view-container.ts b/packages/core/src/browser/view-container.ts
index 3adc265d73857..3ec73cdff7aae 100644
--- a/packages/core/src/browser/view-container.ts
+++ b/packages/core/src/browser/view-container.ts
@@ -30,7 +30,7 @@ import { FrontendApplicationStateService } from './frontend-application-state';
 import { ContextMenuRenderer, Anchor } from './context-menu-renderer';
 import { parseCssMagnitude } from './browser';
 import { TabBarToolbarRegistry, TabBarToolbarFactory, TabBarToolbar, TabBarDelegator, TabBarToolbarItem } from './shell/tab-bar-toolbar';
-import { isEmpty, nls } from '../common';
+import { isEmpty, Is, nls } from '../common';
 import { WidgetManager } from './widget-manager';
 import { Key } from './keys';
 import { ProgressBarFactory } from './progress-bar-factory';
@@ -64,13 +64,13 @@ export interface BadgeWidget {
 
 export namespace DescriptionWidget {
     export function is(arg: unknown): arg is DescriptionWidget {
-        return !!arg && typeof arg === 'object' && 'onDidChangeDescription' in arg;
+        return Is.object(arg) && 'onDidChangeDescription' in arg;
     }
 }
 
 export namespace BadgeWidget {
     export function is(arg: unknown): arg is BadgeWidget {
-        return !!arg && typeof arg === 'object' && 'onDidChangeBadge' in arg;
+        return Is.object(arg) && 'onDidChangeBadge' in arg;
     }
 }
 
diff --git a/packages/core/src/browser/widgets/widget.ts b/packages/core/src/browser/widgets/widget.ts
index 5274d0f2386a6..c29ab8074787f 100644
--- a/packages/core/src/browser/widgets/widget.ts
+++ b/packages/core/src/browser/widgets/widget.ts
@@ -19,7 +19,7 @@
 import { injectable, decorate, unmanaged } from 'inversify';
 import { Title, Widget } from '@phosphor/widgets';
 import { Message, MessageLoop } from '@phosphor/messaging';
-import { Emitter, Event, Disposable, DisposableCollection, MaybePromise } from '../../common';
+import { Emitter, Event, Disposable, DisposableCollection, MaybePromise, Is } from '../../common';
 import { KeyCode, KeysOrKeyCodes } from '../keyboard/keys';
 
 import PerfectScrollbar from 'perfect-scrollbar';
@@ -247,7 +247,7 @@ export interface EventListenerObject<K extends keyof HTMLElementEventMap> {
 }
 export namespace EventListenerObject {
     export function is<K extends keyof HTMLElementEventMap>(listener: unknown): listener is EventListenerObject<K> {
-        return !!listener && typeof listener === 'object' && 'handleEvent' in listener;
+        return Is.object(listener) && 'handleEvent' in listener;
     }
 }
 export type EventListenerOrEventListenerObject<K extends keyof HTMLElementEventMap> = EventListener<K> | EventListenerObject<K>;
diff --git a/packages/core/src/common/cancellation.ts b/packages/core/src/common/cancellation.ts
index 05e93cc18d748..4f48e8aa9ef20 100644
--- a/packages/core/src/common/cancellation.ts
+++ b/packages/core/src/common/cancellation.ts
@@ -19,6 +19,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 import { Event, Emitter } from './event';
+import { Is } from './is';
 
 export interface CancellationToken {
     readonly isCancellationRequested: boolean;
@@ -51,10 +52,9 @@ export namespace CancellationToken {
     });
 
     export function is(value: unknown): value is CancellationToken {
-        const candidate = value as CancellationToken;
-        return candidate && (candidate === CancellationToken.None
-            || candidate === CancellationToken.Cancelled
-            || (typeof candidate.isCancellationRequested === 'boolean' && !!candidate.onCancellationRequested));
+        return Is.object<CancellationToken>(value) && (value === CancellationToken.None
+            || value === CancellationToken.Cancelled
+            || (Is.boolean(value.isCancellationRequested) && !!value.onCancellationRequested));
     }
 }
 
diff --git a/packages/core/src/common/command.ts b/packages/core/src/common/command.ts
index b46a29a510305..4a5bcdcc6eae3 100644
--- a/packages/core/src/common/command.ts
+++ b/packages/core/src/common/command.ts
@@ -20,6 +20,7 @@ import { Disposable, DisposableCollection } from './disposable';
 import { ContributionProvider } from './contribution-provider';
 import { nls } from './nls';
 import debounce = require('p-debounce');
+import { Is } from './is';
 
 /**
  * A command is a unique identifier of a function
@@ -50,7 +51,7 @@ export interface Command {
 export namespace Command {
     /* Determine whether object is a Command */
     export function is(arg: unknown): arg is Command {
-        return !!arg && typeof arg === 'object' && 'id' in arg;
+        return Is.object(arg) && 'id' in arg;
     }
 
     /** Utility function to easily translate commands */
diff --git a/packages/core/src/common/disposable.ts b/packages/core/src/common/disposable.ts
index 379b31006f17f..4d038ea74caa6 100644
--- a/packages/core/src/common/disposable.ts
+++ b/packages/core/src/common/disposable.ts
@@ -14,6 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 import { Event, Emitter } from './event';
+import { Is } from './is';
 
 export interface Disposable {
     /**
@@ -24,7 +25,7 @@ export interface Disposable {
 
 export namespace Disposable {
     export function is(arg: unknown): arg is Disposable {
-        return !!arg && typeof arg === 'object' && typeof (arg as Disposable).dispose === 'function';
+        return Is.object<Disposable>(arg) && Is.func(arg.dispose);
     }
     export function create(func: () => void): Disposable {
         return { dispose: func };
diff --git a/packages/core/src/common/index.ts b/packages/core/src/common/index.ts
index cedfd254d0009..147cab433f6e4 100644
--- a/packages/core/src/common/index.ts
+++ b/packages/core/src/common/index.ts
@@ -43,6 +43,7 @@ export * from './contribution-filter';
 export * from './nls';
 export * from './numbers';
 export * from './performance';
+export * from './is';
 
 import { environment } from '@theia/application-package/lib/environment';
 export { environment };
diff --git a/packages/core/src/common/is.ts b/packages/core/src/common/is.ts
new file mode 100644
index 0000000000000..ca8b949af1f96
--- /dev/null
+++ b/packages/core/src/common/is.ts
@@ -0,0 +1,55 @@
+// *****************************************************************************
+// Copyright (C) 2022 TypeFox and others.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Eclipse Public License v. 2.0 which is available at
+// http://www.eclipse.org/legal/epl-2.0.
+//
+// This Source Code may also be made available under the following Secondary
+// Licenses when the conditions for such availability set forth in the Eclipse
+// Public License v. 2.0 are satisfied: GNU General Public License, version 2
+// with the GNU Classpath Exception which is available at
+// https://www.gnu.org/software/classpath/license.html.
+//
+// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+// *****************************************************************************
+
+export namespace Is {
+
+    export function boolean(value: unknown): value is boolean {
+        return value === true || value === false;
+    }
+
+    export function string(value: unknown): value is string {
+        return typeof value === 'string' || value instanceof String;
+    }
+
+    export function number(value: unknown): value is number {
+        return typeof value === 'number' || value instanceof Number;
+    }
+
+    export function error(value: unknown): value is Error {
+        return value instanceof Error;
+    }
+
+    export function func(value: unknown): value is Function {
+        return typeof value === 'function';
+    }
+
+    export function stringArray(value: unknown): value is string[] {
+        return Array.isArray(value) && value.every(elem => string(elem));
+    }
+
+    export function typedArray<T>(value: unknown, check: (value: unknown) => boolean): value is T[] {
+        return Array.isArray(value) && value.every(check);
+    }
+
+    export function object<T = Record<string | number | symbol, unknown>>(value: unknown): value is T {
+        return typeof value === 'object' && !!value;
+    }
+
+    export function undefined(value: unknown): value is undefined {
+        return typeof value === 'undefined';
+    }
+
+}
diff --git a/packages/core/src/common/keybinding.ts b/packages/core/src/common/keybinding.ts
index cb334bfd7bc28..2037779b6c701 100644
--- a/packages/core/src/common/keybinding.ts
+++ b/packages/core/src/common/keybinding.ts
@@ -13,6 +13,9 @@
 //
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
+
+import { Is } from './is';
+
 /**
  * A Keybinding binds a specific key sequence ({@link Keybinding#keybinding}) to trigger a command ({@link Keybinding#command}). A Keybinding optionally may
  * define a "when clause" ({@link Keybinding#when}) to specify in which context it becomes active.
@@ -102,7 +105,7 @@ export namespace Keybinding {
 
     /* Determine whether object is a KeyBinding */
     export function is(arg: unknown): arg is Keybinding {
-        return !!arg && typeof arg === 'object' && 'command' in arg && 'keybinding' in arg;
+        return Is.object(arg) && 'command' in arg && 'keybinding' in arg;
     }
 }
 
@@ -118,6 +121,6 @@ export interface RawKeybinding extends Omit<Keybinding, 'keybinding'> {
 
 export namespace RawKeybinding {
     export function is(candidate: unknown): candidate is RawKeybinding {
-        return typeof candidate === 'object' && !!candidate && 'command' in candidate && 'key' in candidate;
+        return Is.object(candidate) && 'command' in candidate && 'key' in candidate;
     }
 }
diff --git a/packages/core/src/common/keys.ts b/packages/core/src/common/keys.ts
index 156c2319b3bd9..945a6d184b4ef 100644
--- a/packages/core/src/common/keys.ts
+++ b/packages/core/src/common/keys.ts
@@ -14,6 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import { Is } from './is';
 import { isOSX } from './os';
 
 export type KeySequence = KeyCode[];
@@ -489,7 +490,7 @@ export namespace SpecialCases {
 export namespace Key {
 
     export function isKey(arg: unknown): arg is Key {
-        return !!arg && typeof arg === 'object' && 'code' in arg && 'keyCode' in arg;
+        return Is.object(arg) && 'code' in arg && 'keyCode' in arg;
     }
 
     export function getKey(arg: string | number): Key | undefined {
diff --git a/packages/core/src/common/lsp-types.ts b/packages/core/src/common/lsp-types.ts
index 7af131ef28ae9..a3256046f44f1 100644
--- a/packages/core/src/common/lsp-types.ts
+++ b/packages/core/src/common/lsp-types.ts
@@ -15,6 +15,7 @@
 // *****************************************************************************
 
 import { Range } from 'vscode-languageserver-protocol';
+import { Is } from './is';
 
 export interface TextDocumentContentChangeDelta {
     readonly range: Range;
@@ -24,12 +25,10 @@ export interface TextDocumentContentChangeDelta {
 export namespace TextDocumentContentChangeDelta {
 
     export function is(arg: unknown): arg is TextDocumentContentChangeDelta {
-        const changeDelta = arg as TextDocumentContentChangeDelta;
-        return !!changeDelta
-            && typeof changeDelta === 'object'
-            && typeof changeDelta.text === 'string'
-            && (typeof changeDelta.rangeLength === 'number' || typeof changeDelta.rangeLength === 'undefined')
-            && Range.is(changeDelta.range);
+        return Is.object<TextDocumentContentChangeDelta>(arg)
+            && Is.string(arg.text)
+            && (Is.number(arg.rangeLength) || Is.undefined(arg.rangeLength))
+            && Range.is(arg.range);
     }
 
 }
diff --git a/packages/core/src/common/markdown-rendering/markdown-string.ts b/packages/core/src/common/markdown-rendering/markdown-string.ts
index 5bb94a4a23553..d745000b9cbea 100644
--- a/packages/core/src/common/markdown-rendering/markdown-string.ts
+++ b/packages/core/src/common/markdown-rendering/markdown-string.ts
@@ -14,6 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import { Is } from '../is';
 import { escapeRegExpCharacters } from '../strings';
 import { UriComponents } from '../uri';
 import { escapeIcons } from './icon-utilities';
@@ -37,8 +38,7 @@ export namespace MarkdownString {
      * @returns whether the candidate satisfies the interface of a markdown string
      */
     export function is(candidate: unknown): candidate is MarkdownString {
-        const maybeMarkdownString = candidate as MarkdownString;
-        return typeof maybeMarkdownString === 'object' && !!maybeMarkdownString && typeof maybeMarkdownString.value === 'string';
+        return Is.object<MarkdownString>(candidate) && Is.string(candidate.value);
     }
 }
 
diff --git a/packages/core/src/common/menu/menu-types.ts b/packages/core/src/common/menu/menu-types.ts
index c763c26a8e649..e5b0479cdab3f 100644
--- a/packages/core/src/common/menu/menu-types.ts
+++ b/packages/core/src/common/menu/menu-types.ts
@@ -14,6 +14,8 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import { Is } from '../is';
+
 /**
  * A menu entry representing an action, e.g. "New File".
  */
@@ -37,7 +39,7 @@ export interface MenuAction extends MenuNodeRenderingData, Pick<MenuNodeMetadata
 export namespace MenuAction {
     /* Determine whether object is a MenuAction */
     export function is(arg: unknown): arg is MenuAction {
-        return !!arg && typeof arg === 'object' && 'commandId' in arg;
+        return Is.object(arg) && 'commandId' in arg;
     }
 }
 
diff --git a/packages/core/src/common/objects.ts b/packages/core/src/common/objects.ts
index 183fc81bdfef8..c5061026c4fbd 100644
--- a/packages/core/src/common/objects.ts
+++ b/packages/core/src/common/objects.ts
@@ -14,8 +14,10 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import { Is } from './is';
+
 export function deepClone<T>(obj: T): T {
-    if (!obj || typeof obj !== 'object') {
+    if (!Is.object(obj)) {
         return obj;
     }
     if (obj instanceof RegExp) {
@@ -24,9 +26,8 @@ export function deepClone<T>(obj: T): T {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     const result: any = Array.isArray(obj) ? [] : {};
     Object.keys(obj).forEach((key: string) => {
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        const prop = (<any>obj)[key];
-        if (prop && typeof prop === 'object') {
+        const prop = obj[key];
+        if (Is.object(prop)) {
             result[key] = deepClone(prop);
         } else {
             result[key] = prop;
@@ -36,7 +37,7 @@ export function deepClone<T>(obj: T): T {
 }
 
 export function deepFreeze<T>(obj: T): T {
-    if (!obj || typeof obj !== 'object') {
+    if (!Is.object(obj)) {
         return obj;
     }
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -47,7 +48,7 @@ export function deepFreeze<T>(obj: T): T {
         for (const key in objectToFreeze) {
             if (_hasOwnProperty.call(objectToFreeze, key)) {
                 const prop = objectToFreeze[key];
-                if (typeof prop === 'object' && !Object.isFrozen(prop)) {
+                if (Is.object(prop) && !Object.isFrozen(prop)) {
                     stack.push(prop);
                 }
             }
diff --git a/packages/core/src/common/preferences/preference-schema.ts b/packages/core/src/common/preferences/preference-schema.ts
index f5a41cf50faca..2fbba9e4f78b4 100644
--- a/packages/core/src/common/preferences/preference-schema.ts
+++ b/packages/core/src/common/preferences/preference-schema.ts
@@ -17,6 +17,7 @@
 /* eslint-disable @typescript-eslint/no-explicit-any */
 
 import { JSONValue } from '@phosphor/coreutils';
+import { Is } from '../is';
 import { IJSONSchema } from '../json-schema';
 import { PreferenceScope } from './preference-scope';
 
@@ -28,7 +29,7 @@ export interface PreferenceSchema {
 }
 export namespace PreferenceSchema {
     export function is(obj: unknown): obj is PreferenceSchema {
-        return !!obj && typeof obj === 'object' && ('properties' in obj) && PreferenceSchemaProperties.is((obj as PreferenceSchema).properties);
+        return Is.object<PreferenceSchema>(obj) && PreferenceSchemaProperties.is(obj.properties);
     }
     export function getDefaultScope(schema: PreferenceSchema): PreferenceScope {
         let defaultScope: PreferenceScope = PreferenceScope.Workspace;
@@ -46,7 +47,7 @@ export interface PreferenceSchemaProperties {
 }
 export namespace PreferenceSchemaProperties {
     export function is(obj: unknown): obj is PreferenceSchemaProperties {
-        return !!obj && typeof obj === 'object';
+        return Is.object(obj);
     }
 }
 
@@ -86,7 +87,7 @@ export namespace PreferenceDataProperty {
     export function fromPreferenceSchemaProperty(schemaProps: PreferenceSchemaProperty, defaultScope: PreferenceScope = PreferenceScope.Workspace): PreferenceDataProperty {
         if (!schemaProps.scope) {
             schemaProps.scope = defaultScope;
-        } else if (typeof schemaProps.scope === 'string') {
+        } else if (Is.string(schemaProps.scope)) {
             return Object.assign(schemaProps, { scope: PreferenceScope.fromString(schemaProps.scope) || defaultScope });
         }
         return <PreferenceDataProperty>schemaProps;
diff --git a/packages/core/src/common/promise-util.ts b/packages/core/src/common/promise-util.ts
index 301ac51254229..579c991565cff 100644
--- a/packages/core/src/common/promise-util.ts
+++ b/packages/core/src/common/promise-util.ts
@@ -17,6 +17,7 @@
 import { Disposable } from './disposable';
 import { Event } from './event';
 import { CancellationToken, CancellationError, cancelled } from './cancellation';
+import { Is } from './is';
 
 /**
  * Simple implementation of the deferred pattern.
@@ -126,5 +127,5 @@ export function waitForEvent<T>(event: Event<T>, ms: number, thisArg?: any, disp
 }
 
 export function isThenable<T>(obj: unknown): obj is Promise<T> {
-    return typeof obj === 'object' && !!obj && typeof (obj as Promise<unknown>).then === 'function';
+    return Is.object<Promise<unknown>>(obj) && Is.func(obj.then);
 }
diff --git a/packages/core/src/common/selection.ts b/packages/core/src/common/selection.ts
index 62deee5e06a5e..0f59a90d2ce43 100644
--- a/packages/core/src/common/selection.ts
+++ b/packages/core/src/common/selection.ts
@@ -14,6 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import { Is } from './is';
 import URI from './uri';
 
 export interface UriSelection {
@@ -23,7 +24,7 @@ export interface UriSelection {
 export namespace UriSelection {
 
     export function is(arg: unknown): arg is UriSelection {
-        return !!arg && typeof arg === 'object' && ('uri' in arg) && (arg as UriSelection).uri instanceof URI;
+        return Is.object<UriSelection>(arg) && arg.uri instanceof URI;
     }
 
     export function getUri(selection: unknown): URI | undefined {
diff --git a/packages/core/src/common/uri-command-handler.ts b/packages/core/src/common/uri-command-handler.ts
index a15967600d7c5..7d51f20efe11e 100644
--- a/packages/core/src/common/uri-command-handler.ts
+++ b/packages/core/src/common/uri-command-handler.ts
@@ -21,6 +21,7 @@ import { UriSelection } from '../common/selection';
 import { CommandHandler } from './command';
 import URI from './uri';
 import { MaybeArray } from './types';
+import { Is } from './is';
 
 export interface UriCommandHandler<T extends MaybeArray<URI>> extends CommandHandler {
 
@@ -59,7 +60,7 @@ export class UriAwareCommandHandler<T extends MaybeArray<URI>> implements UriCom
     protected getUri(...args: any[]): T | undefined {
         const [maybeUriArray] = args;
         const firstArgIsOK = this.isMulti()
-            ? Array.isArray(maybeUriArray) && maybeUriArray.every(uri => uri instanceof URI)
+            ? Is.typedArray(maybeUriArray, uri => uri instanceof URI)
             : maybeUriArray instanceof URI;
 
         if (firstArgIsOK) {
diff --git a/packages/core/src/electron-node/token/electron-token-validator.ts b/packages/core/src/electron-node/token/electron-token-validator.ts
index 6b58d4b009472..9ab17dd1edddf 100644
--- a/packages/core/src/electron-node/token/electron-token-validator.ts
+++ b/packages/core/src/electron-node/token/electron-token-validator.ts
@@ -18,7 +18,7 @@ import * as http from 'http';
 import * as cookie from 'cookie';
 import * as crypto from 'crypto';
 import { injectable, postConstruct } from 'inversify';
-import { MaybePromise } from '../../common';
+import { Is, MaybePromise } from '../../common';
 import { ElectronSecurityToken } from '../../electron-common/electron-token';
 import { WsRequestValidatorContribution } from '../../node/ws-request-validators';
 
@@ -44,9 +44,9 @@ export class ElectronTokenValidator implements WsRequestValidatorContribution {
      */
     allowRequest(request: http.IncomingMessage): boolean {
         const cookieHeader = request.headers.cookie;
-        if (typeof cookieHeader === 'string') {
+        if (Is.string(cookieHeader)) {
             const token = cookie.parse(cookieHeader)[ElectronSecurityToken];
-            if (typeof token === 'string') {
+            if (Is.string(token)) {
                 return this.isTokenValid(JSON.parse(token));
             }
         }
@@ -60,10 +60,8 @@ export class ElectronTokenValidator implements WsRequestValidatorContribution {
      *
      * @param token Parsed object sent by the client as the token.
      */
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    isTokenValid(token: any): boolean {
-        // eslint-disable-next-line no-null/no-null
-        if (typeof token === 'object' && token !== null && typeof token.value === 'string') {
+    isTokenValid(token: unknown): boolean {
+        if (Is.object(token) && Is.string(token.value)) {
             try {
                 const received = Buffer.from(token.value, 'utf8');
                 const expected = Buffer.from(this.electronSecurityToken!.value, 'utf8');
diff --git a/packages/core/src/node/i18n/localization-contribution.ts b/packages/core/src/node/i18n/localization-contribution.ts
index 078fb30970c09..5a87189bb7635 100644
--- a/packages/core/src/node/i18n/localization-contribution.ts
+++ b/packages/core/src/node/i18n/localization-contribution.ts
@@ -16,7 +16,7 @@
 
 import * as fs from 'fs-extra';
 import { inject, injectable, named } from 'inversify';
-import { ContributionProvider } from '../../common';
+import { ContributionProvider, Is } from '../../common';
 import { LanguageInfo, Localization } from '../../common/i18n/localization';
 import { LocalizationProvider } from './localization-provider';
 
@@ -79,12 +79,12 @@ export class LocalizationRegistry {
     }
 
     protected flattenTranslations(localization: unknown): Record<string, string> {
-        if (typeof localization === 'object' && localization) {
+        if (Is.object(localization)) {
             const record: Record<string, string> = {};
             for (const [key, value] of Object.entries(localization)) {
                 if (typeof value === 'string') {
                     record[key] = value;
-                } else if (value && typeof value === 'object') {
+                } else if (Is.object(value)) {
                     const flattened = this.flattenTranslations(value);
                     for (const [flatKey, flatValue] of Object.entries(flattened)) {
                         record[`${key}/${flatKey}`] = flatValue;
diff --git a/packages/debug/src/browser/breakpoint/breakpoint-marker.ts b/packages/debug/src/browser/breakpoint/breakpoint-marker.ts
index 74e45500b9a43..615acd0871359 100644
--- a/packages/debug/src/browser/breakpoint/breakpoint-marker.ts
+++ b/packages/debug/src/browser/breakpoint/breakpoint-marker.ts
@@ -18,6 +18,7 @@ import { UUID } from '@theia/core/shared/@phosphor/coreutils';
 import URI from '@theia/core/lib/common/uri';
 import { Marker } from '@theia/markers/lib/common/marker';
 import { DebugProtocol } from '@vscode/debugprotocol/lib/debugProtocol';
+import { Is } from '@theia/core/lib/common/is';
 
 export const BREAKPOINT_KIND = 'breakpoint';
 
@@ -96,8 +97,7 @@ export namespace InstructionBreakpoint {
         };
     }
 
-    export function is(thing: BaseBreakpoint): thing is InstructionBreakpoint {
-        const candidate = thing as InstructionBreakpoint;
-        return 'instructionReference' in candidate && typeof candidate.instructionReference === 'string';
+    export function is(arg: BaseBreakpoint): arg is InstructionBreakpoint {
+        return Is.object<InstructionBreakpoint>(arg) && Is.string(arg.instructionReference);
     }
 }
diff --git a/packages/debug/src/browser/debug-configuration-model.ts b/packages/debug/src/browser/debug-configuration-model.ts
index 90260b3aedf6f..718d72c9aa5fd 100644
--- a/packages/debug/src/browser/debug-configuration-model.ts
+++ b/packages/debug/src/browser/debug-configuration-model.ts
@@ -20,6 +20,7 @@ import { Disposable, DisposableCollection } from '@theia/core/lib/common/disposa
 import { DebugConfiguration } from '../common/debug-common';
 import { PreferenceService } from '@theia/core/lib/browser/preferences/preference-service';
 import { DebugCompound } from '../common/debug-compound';
+import { Is } from '@theia/core/lib/common/is';
 
 export class DebugConfigurationModel implements Disposable {
 
@@ -71,7 +72,7 @@ export class DebugConfigurationModel implements Disposable {
         const configurations: DebugConfiguration[] = [];
         // eslint-disable-next-line @typescript-eslint/no-explicit-any
         const { configUri, value } = this.preferences.resolve<any>('launch', undefined, this.workspaceFolderUri);
-        if (value && typeof value === 'object' && Array.isArray(value.configurations)) {
+        if (Is.object(value) && Array.isArray(value.configurations)) {
             for (const configuration of value.configurations) {
                 if (DebugConfiguration.is(configuration)) {
                     configurations.push(configuration);
@@ -79,7 +80,7 @@ export class DebugConfigurationModel implements Disposable {
             }
         }
         const compounds: DebugCompound[] = [];
-        if (value && typeof value === 'object' && Array.isArray(value.compounds)) {
+        if (Is.object(value) && Array.isArray(value.compounds)) {
             for (const compound of value.compounds) {
                 if (DebugCompound.is(compound)) {
                     compounds.push(compound);
diff --git a/packages/debug/src/browser/editor/debug-editor-model.ts b/packages/debug/src/browser/editor/debug-editor-model.ts
index 00060712ffd55..0264e0eae322c 100644
--- a/packages/debug/src/browser/editor/debug-editor-model.ts
+++ b/packages/debug/src/browser/editor/debug-editor-model.ts
@@ -20,6 +20,7 @@ import * as monaco from '@theia/monaco-editor-core';
 import { IConfigurationService } from '@theia/monaco-editor-core/esm/vs/platform/configuration/common/configuration';
 import { StandaloneCodeEditor } from '@theia/monaco-editor-core/esm/vs/editor/standalone/browser/standaloneCodeEditor';
 import { IDecorationOptions } from '@theia/monaco-editor-core/esm/vs/editor/common/editorCommon';
+import { IEditorHoverOptions } from '@theia/monaco-editor-core/esm/vs/editor/common/config/editorOptions';
 import URI from '@theia/core/lib/common/uri';
 import { Disposable, DisposableCollection, MenuPath, isOSX } from '@theia/core';
 import { ContextMenuRenderer } from '@theia/core/lib/browser';
@@ -146,7 +147,7 @@ export class DebugEditorModel implements Disposable {
                     resource: model.uri,
                     overrideIdentifier: model.getLanguageId(),
                 };
-                const { enabled, delay, sticky } = this.configurationService.getValue('editor.hover', overrides);
+                const { enabled, delay, sticky } = this.configurationService.getValue<IEditorHoverOptions>('editor.hover', overrides);
                 codeEditor.updateOptions({
                     hover: {
                         enabled,
diff --git a/packages/debug/src/common/debug-compound.ts b/packages/debug/src/common/debug-compound.ts
index d019e69b9a142..4afeecf1e538f 100644
--- a/packages/debug/src/common/debug-compound.ts
+++ b/packages/debug/src/common/debug-compound.ts
@@ -14,6 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import { Is } from '@theia/core/lib/common/is';
 import { TaskIdentifier } from '@theia/task/lib/common';
 
 export const defaultCompound: DebugCompound = { name: 'Compound', configurations: [] };
@@ -27,6 +28,6 @@ export interface DebugCompound {
 
 export namespace DebugCompound {
     export function is(arg: unknown): arg is DebugCompound {
-        return !!arg && typeof arg === 'object' && 'name' in arg && 'configurations' in arg;
+        return Is.object(arg) && 'name' in arg && 'configurations' in arg;
     }
 }
diff --git a/packages/debug/src/common/debug-configuration.ts b/packages/debug/src/common/debug-configuration.ts
index 6abd0a8a725d6..cfdebb279ad0f 100644
--- a/packages/debug/src/common/debug-configuration.ts
+++ b/packages/debug/src/common/debug-configuration.ts
@@ -13,6 +13,7 @@
 //
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
+import { Is } from '@theia/core/lib/common/is';
 import { TaskIdentifier } from '@theia/task/lib/common';
 /* eslint-disable @typescript-eslint/no-explicit-any */
 
@@ -72,7 +73,7 @@ export interface DebugConfiguration {
 }
 export namespace DebugConfiguration {
     export function is(arg: unknown): arg is DebugConfiguration {
-        return !!arg && typeof arg === 'object' && 'type' in arg && 'name' in arg && 'request' in arg;
+        return Is.object(arg) && 'type' in arg && 'name' in arg && 'request' in arg;
     }
 }
 
diff --git a/packages/debug/src/node/debug-adapter-factory.ts b/packages/debug/src/node/debug-adapter-factory.ts
index dd0b0b9026e3f..756397f10725c 100644
--- a/packages/debug/src/node/debug-adapter-factory.ts
+++ b/packages/debug/src/node/debug-adapter-factory.ts
@@ -41,6 +41,7 @@ import {
 import { DebugAdapterSessionImpl } from '../common/debug-adapter-session';
 import { environment } from '@theia/core/shared/@theia/application-package';
 import { ProcessDebugAdapter, SocketDebugAdapter } from './stream-debug-adapter';
+import { Is } from '@theia/core/lib/common/is';
 
 /**
  * [DebugAdapterFactory](#DebugAdapterFactory) implementation based on
@@ -67,7 +68,7 @@ export class LaunchBasedDebugAdapterFactory implements DebugAdapterFactory {
 
     private childProcess(executable: DebugAdapterExecutable): RawProcess {
         const isForkOptions = (forkOptions: unknown): forkOptions is RawForkOptions =>
-            !!forkOptions && typeof forkOptions === 'object' && 'modulePath' in forkOptions;
+            Is.object(forkOptions) && 'modulePath' in forkOptions;
 
         const processOptions: RawProcessOptions | RawForkOptions = { ...executable };
         const options: { stdio: (string | number)[], env?: object, execArgv?: string[] } = { stdio: ['pipe', 'pipe', 2] };
diff --git a/packages/editor/src/browser/editor.ts b/packages/editor/src/browser/editor.ts
index 12a1cf85c21e2..cddc544996006 100644
--- a/packages/editor/src/browser/editor.ts
+++ b/packages/editor/src/browser/editor.ts
@@ -17,7 +17,7 @@
 import { Position, Range, Location } from '@theia/core/shared/vscode-languageserver-protocol';
 import * as lsp from '@theia/core/shared/vscode-languageserver-protocol';
 import URI from '@theia/core/lib/common/uri';
-import { Event, Disposable, TextDocumentContentChangeDelta, Reference } from '@theia/core/lib/common';
+import { Event, Disposable, TextDocumentContentChangeDelta, Reference, Is } from '@theia/core/lib/common';
 import { Saveable, Navigatable, Widget } from '@theia/core/lib/browser';
 import { EditorDecoration } from './decorations';
 
@@ -331,8 +331,8 @@ export interface ReplaceOperation {
 }
 
 export namespace TextEditorSelection {
-    export function is(e: unknown): e is TextEditorSelection {
-        return !!e && typeof e === 'object' && (e as TextEditorSelection).uri instanceof URI;
+    export function is(arg: unknown): arg is TextEditorSelection {
+        return Is.object<TextEditorSelection>(arg) && arg.uri instanceof URI;
     }
 }
 
diff --git a/packages/filesystem/src/browser/file-selection.ts b/packages/filesystem/src/browser/file-selection.ts
index 81aefa5942992..9acedd810c259 100644
--- a/packages/filesystem/src/browser/file-selection.ts
+++ b/packages/filesystem/src/browser/file-selection.ts
@@ -16,6 +16,7 @@
 
 import { SelectionService } from '@theia/core/lib/common/selection-service';
 import { SelectionCommandHandler } from '@theia/core/lib/common/selection-command-handler';
+import { Is } from '@theia/core/lib/common/is';
 import { FileStat } from '../common/files';
 
 export interface FileSelection {
@@ -23,7 +24,7 @@ export interface FileSelection {
 }
 export namespace FileSelection {
     export function is(arg: unknown): arg is FileSelection {
-        return !!arg && typeof arg === 'object' && ('fileStat' in arg) && FileStat.is((arg as FileSelection).fileStat);
+        return Is.object<FileSelection>(arg) && FileStat.is(arg.fileStat);
     }
     export class CommandHandler extends SelectionCommandHandler<FileSelection> {
 
diff --git a/packages/filesystem/src/browser/file-tree/file-tree.ts b/packages/filesystem/src/browser/file-tree/file-tree.ts
index 733ec2766e9c4..b933ad7c3d1a3 100644
--- a/packages/filesystem/src/browser/file-tree/file-tree.ts
+++ b/packages/filesystem/src/browser/file-tree/file-tree.ts
@@ -16,6 +16,7 @@
 
 import { injectable, inject } from '@theia/core/shared/inversify';
 import URI from '@theia/core/lib/common/uri';
+import { Is } from '@theia/core/lib/common/is';
 import { TreeNode, CompositeTreeNode, SelectableTreeNode, ExpandableTreeNode, TreeImpl } from '@theia/core/lib/browser';
 import { Mutable } from '@theia/core/lib/common/types';
 import { FileStat, Stat, FileType, FileOperationError, FileOperationResult } from '../../common/files';
@@ -102,7 +103,7 @@ export interface FileStatNode extends SelectableTreeNode, Mutable<UriSelection>,
 }
 export namespace FileStatNode {
     export function is(node: unknown): node is FileStatNode {
-        return !!node && typeof node === 'object' && 'fileStat' in node;
+        return Is.object(node) && 'fileStat' in node;
     }
 
     export function getUri(node: TreeNode | undefined): string | undefined {
@@ -120,7 +121,7 @@ export type FileStatNodeData = Omit<FileStatNode, 'uri' | 'fileStat'> & {
 };
 export namespace FileStatNodeData {
     export function is(node: unknown): node is FileStatNodeData {
-        return !!node && typeof node === 'object' && 'uri' in node && ('fileStat' in node || 'stat' in node);
+        return Is.object(node) && 'uri' in node && ('fileStat' in node || 'stat' in node);
     }
 }
 
diff --git a/packages/filesystem/src/common/download/file-download-data.ts b/packages/filesystem/src/common/download/file-download-data.ts
index 048e8da47bce9..b47d14b52ff09 100644
--- a/packages/filesystem/src/common/download/file-download-data.ts
+++ b/packages/filesystem/src/common/download/file-download-data.ts
@@ -14,12 +14,14 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import { Is } from '@theia/core/lib/common/is';
+
 export interface FileDownloadData {
     readonly uris: string[];
 }
 
 export namespace FileDownloadData {
     export function is(arg: unknown): arg is FileDownloadData {
-        return !!arg && typeof arg === 'object' && 'uris' in arg;
+        return Is.object(arg) && 'uris' in arg;
     }
 }
diff --git a/packages/filesystem/src/common/files.ts b/packages/filesystem/src/common/files.ts
index 2dfed8108bb9c..f41ffef0240d4 100644
--- a/packages/filesystem/src/common/files.ts
+++ b/packages/filesystem/src/common/files.ts
@@ -26,6 +26,7 @@ import { BinaryBuffer, BinaryBufferReadableStream } from '@theia/core/lib/common
 import type { TextDocumentContentChangeEvent } from '@theia/core/shared/vscode-languageserver-protocol';
 import { ReadableStreamEvents } from '@theia/core/lib/common/stream';
 import { CancellationToken } from '@theia/core/lib/common/cancellation';
+import { Is } from '@theia/core/lib/common/is';
 
 export const enum FileOperation {
     CREATE,
@@ -201,9 +202,9 @@ export interface BaseStat {
 }
 export namespace BaseStat {
     export function is(arg: unknown): arg is BaseStat {
-        return !!arg && typeof arg === 'object'
-            && ('resource' in arg && (arg as BaseStat).resource instanceof URI)
-            && ('name' in arg && typeof (arg as BaseStat).name === 'string');
+        return Is.object<BaseStat>(arg)
+            && arg.resource instanceof URI
+            && typeof arg.name === 'string';
     }
 }
 
diff --git a/packages/git/src/common/git-model.ts b/packages/git/src/common/git-model.ts
index 894a5488f978e..d23c5ad10385a 100644
--- a/packages/git/src/common/git-model.ts
+++ b/packages/git/src/common/git-model.ts
@@ -15,8 +15,7 @@
 // *****************************************************************************
 
 import URI from '@theia/core/lib/common/uri';
-import { Path } from '@theia/core';
-import { nls } from '@theia/core/lib/common/nls';
+import { Is, Path, nls } from '@theia/core';
 
 export interface WorkingDirectoryStatus {
 
@@ -213,7 +212,7 @@ export namespace Repository {
         return repository === repository2;
     }
     export function is(repository: unknown): repository is Repository {
-        return !!repository && typeof repository === 'object' && 'localUri' in repository;
+        return Is.object(repository) && 'localUri' in repository;
     }
     export function relativePath(repository: Repository | URI, uri: URI | string): Path | undefined {
         const repositoryUri = new URI(Repository.is(repository) ? repository.localUri : String(repository));
diff --git a/packages/git/src/common/git-watcher.ts b/packages/git/src/common/git-watcher.ts
index a078e376f3cb3..4f511490bf941 100644
--- a/packages/git/src/common/git-watcher.ts
+++ b/packages/git/src/common/git-watcher.ts
@@ -15,7 +15,7 @@
 // *****************************************************************************
 
 import { injectable, inject } from '@theia/core/shared/inversify';
-import { JsonRpcServer, JsonRpcProxy } from '@theia/core';
+import { JsonRpcServer, JsonRpcProxy, Is } from '@theia/core';
 import { Repository, WorkingDirectoryStatus } from './git-model';
 import { Disposable, DisposableCollection, Emitter, Event } from '@theia/core/lib/common';
 
@@ -48,7 +48,7 @@ export namespace GitStatusChangeEvent {
      * @param event the argument to check whether it is a Git status change event or not.
      */
     export function is(event: unknown): event is GitStatusChangeEvent {
-        return !!event && typeof event === 'object' && ('source' in event) && ('status' in event);
+        return Is.object(event) && ('source' in event) && ('status' in event);
     }
 
 }
diff --git a/packages/git/src/common/git.ts b/packages/git/src/common/git.ts
index 9ed52916f2b35..996977efd878a 100644
--- a/packages/git/src/common/git.ts
+++ b/packages/git/src/common/git.ts
@@ -15,7 +15,7 @@
 // *****************************************************************************
 
 import { ChildProcess } from 'child_process';
-import { Disposable } from '@theia/core';
+import { Disposable, Is } from '@theia/core';
 import {
     Repository, WorkingDirectoryStatus, Branch, GitResult, GitError, GitFileStatus,
     GitFileChange, CommitWithChanges, GitFileBlame, Remote as RemoteModel, StashEntry
@@ -854,42 +854,42 @@ export namespace GitUtils {
      * `true` if the argument is an option for renaming an existing branch in the repository.
      */
     export function isBranchRename(arg: unknown): arg is Git.Options.BranchCommand.Rename {
-        return !!arg && typeof arg === 'object' && ('newName' in arg);
+        return Is.object(arg) && 'newName' in arg;
     }
 
     /**
      * `true` if the argument is an option for deleting an existing branch in the repository.
      */
     export function isBranchDelete(arg: unknown): arg is Git.Options.BranchCommand.Delete {
-        return !!arg && typeof arg === 'object' && ('toDelete' in arg);
+        return Is.object(arg) && 'toDelete' in arg;
     }
 
     /**
      * `true` if the argument is an option for creating a new branch in the repository.
      */
     export function isBranchCreate(arg: unknown): arg is Git.Options.BranchCommand.Create {
-        return !!arg && typeof arg === 'object' && ('toCreate' in arg);
+        return Is.object(arg) && 'toCreate' in arg;
     }
 
     /**
      * `true` if the argument is an option for listing the branches in a repository.
      */
     export function isBranchList(arg: unknown): arg is Git.Options.BranchCommand.List {
-        return !!arg && typeof arg === 'object' && ('type' in arg);
+        return Is.object(arg) && 'type' in arg;
     }
 
     /**
      * `true` if the argument is an option for checking out a new local branch.
      */
     export function isBranchCheckout(arg: unknown): arg is Git.Options.Checkout.CheckoutBranch {
-        return !!arg && typeof arg === 'object' && ('branch' in arg);
+        return Is.object(arg) && 'branch' in arg;
     }
 
     /**
      * `true` if the argument is an option for checking out a working tree file.
      */
     export function isWorkingTreeFileCheckout(arg: unknown): arg is Git.Options.Checkout.WorkingTreeFile {
-        return !!arg && typeof arg === 'object' && ('paths' in arg);
+        return Is.object(arg) && 'paths' in arg;
     }
 
     /**
diff --git a/packages/markers/src/browser/problem/problem-selection.ts b/packages/markers/src/browser/problem/problem-selection.ts
index 39552b170de0a..f2e74eda1981e 100644
--- a/packages/markers/src/browser/problem/problem-selection.ts
+++ b/packages/markers/src/browser/problem/problem-selection.ts
@@ -16,6 +16,7 @@
 
 import { SelectionService } from '@theia/core/lib/common/selection-service';
 import { SelectionCommandHandler } from '@theia/core/lib/common/selection-command-handler';
+import { Is } from '@theia/core/lib/common/is';
 import { Marker } from '../../common/marker';
 import { ProblemMarker } from '../../common/problem-marker';
 
@@ -24,7 +25,7 @@ export interface ProblemSelection {
 }
 export namespace ProblemSelection {
     export function is(arg: unknown): arg is ProblemSelection {
-        return !!arg && typeof arg === 'object' && ('marker' in arg) && ProblemMarker.is((arg as ProblemSelection).marker);
+        return Is.object<ProblemSelection>(arg) && ProblemMarker.is(arg.marker);
     }
 
     export class CommandHandler extends SelectionCommandHandler<ProblemSelection> {
diff --git a/packages/monaco/src/browser/monaco-indexed-db.ts b/packages/monaco/src/browser/monaco-indexed-db.ts
index 2e29b183b10f4..04b76e64ecb0f 100644
--- a/packages/monaco/src/browser/monaco-indexed-db.ts
+++ b/packages/monaco/src/browser/monaco-indexed-db.ts
@@ -21,7 +21,7 @@ import * as monaco from '@theia/monaco-editor-core';
 import { injectable } from '@theia/core/shared/inversify';
 import type { ThemeMix } from './textmate/monaco-theme-types';
 import { Theme } from '@theia/core/lib/common/theme';
-import { Emitter, Event } from '@theia/core';
+import { Emitter, Event, Is } from '@theia/core';
 
 let _monacoDB: Promise<idb.IDBPDatabase> | undefined;
 if ('indexedDB' in window) {
@@ -45,7 +45,7 @@ export interface MonacoThemeState {
 }
 export namespace MonacoThemeState {
     export function is(state: unknown): state is MonacoThemeState {
-        return !!state && typeof state === 'object' && 'id' in state && 'label' in state && 'uiTheme' in state && 'data' in state;
+        return Is.object(state) && 'id' in state && 'label' in state && 'uiTheme' in state && 'data' in state;
     }
 }
 
diff --git a/packages/monaco/src/browser/monaco-snippet-suggest-provider.ts b/packages/monaco/src/browser/monaco-snippet-suggest-provider.ts
index 6215a39aebaa7..f471521c51cef 100644
--- a/packages/monaco/src/browser/monaco-snippet-suggest-provider.ts
+++ b/packages/monaco/src/browser/monaco-snippet-suggest-provider.ts
@@ -26,6 +26,7 @@ import { FileService } from '@theia/filesystem/lib/browser/file-service';
 import { FileOperationError } from '@theia/filesystem/lib/common/files';
 import * as monaco from '@theia/monaco-editor-core';
 import { SnippetParser } from '@theia/monaco-editor-core/esm/vs/editor/contrib/snippet/browser/snippetParser';
+import { Is } from '@theia/core/lib/common/is';
 
 @injectable()
 export class MonacoSnippetSuggestProvider implements monaco.languages.CompletionItemProvider {
@@ -191,15 +192,11 @@ export class MonacoSnippetSuggestProvider implements monaco.languages.Completion
         return toDispose;
     }
     protected parseSnippets(snippets: JsonSerializedSnippets | undefined, accept: (name: string, snippet: JsonSerializedSnippet) => void): void {
-        if (typeof snippets === 'object') {
-            // eslint-disable-next-line guard-for-in
-            for (const name in snippets) {
-                const scopeOrTemplate = snippets[name];
-                if (JsonSerializedSnippet.is(scopeOrTemplate)) {
-                    accept(name, scopeOrTemplate);
-                } else {
-                    this.parseSnippets(scopeOrTemplate, accept);
-                }
+        for (const [name, scopeOrTemplate] of Object.entries(snippets ?? {})) {
+            if (JsonSerializedSnippet.is(scopeOrTemplate)) {
+                accept(name, scopeOrTemplate);
+            } else {
+                this.parseSnippets(scopeOrTemplate, accept);
             }
         }
     }
@@ -250,7 +247,7 @@ export interface JsonSerializedSnippet {
 }
 export namespace JsonSerializedSnippet {
     export function is(obj: unknown): obj is JsonSerializedSnippet {
-        return !!obj && typeof obj === 'object' && 'body' in obj && 'prefix' in obj;
+        return Is.object(obj) && 'body' in obj && 'prefix' in obj;
     }
 }
 
diff --git a/packages/monaco/src/browser/monaco-workspace.ts b/packages/monaco/src/browser/monaco-workspace.ts
index 8e785d61a49d2..fde4a258bf668 100644
--- a/packages/monaco/src/browser/monaco-workspace.ts
+++ b/packages/monaco/src/browser/monaco-workspace.ts
@@ -37,6 +37,7 @@ import {
 import { IEditorWorkerService } from '@theia/monaco-editor-core/esm/vs/editor/common/services/editorWorker';
 import { StandaloneServices } from '@theia/monaco-editor-core/esm/vs/editor/standalone/browser/standaloneServices';
 import { EndOfLineSequence } from '@theia/monaco-editor-core/esm/vs/editor/common/model';
+import { Is } from '@theia/core/lib/common/is';
 
 export namespace WorkspaceFileEdit {
     export function is(arg: Edit): arg is monaco.languages.WorkspaceFileEdit {
@@ -47,12 +48,9 @@ export namespace WorkspaceFileEdit {
 
 export namespace WorkspaceTextEdit {
     export function is(arg: Edit): arg is monaco.languages.WorkspaceTextEdit {
-        return !!arg && typeof arg === 'object'
-            && 'resource' in arg
+        return Is.object<monaco.languages.WorkspaceTextEdit>(arg)
             && monaco.Uri.isUri(arg.resource)
-            && 'edit' in arg
-            && arg.edit !== null
-            && typeof arg.edit === 'object';
+            && Is.object(arg.edit);
     }
 }
 
@@ -60,8 +58,7 @@ export type Edit = monaco.languages.WorkspaceFileEdit | monaco.languages.Workspa
 
 export namespace ResourceFileEdit {
     export function is(arg: ResourceEdit): arg is MonacoResourceFileEdit {
-        return typeof arg === 'object' && (('oldResource' in arg) && monaco.Uri.isUri((arg as MonacoResourceFileEdit).oldResource)) ||
-            ('newResource' in arg && monaco.Uri.isUri((arg as MonacoResourceFileEdit).newResource));
+        return Is.object<MonacoResourceFileEdit>(arg) && (monaco.Uri.isUri(arg.oldResource) || monaco.Uri.isUri(arg.newResource));
     }
 }
 
diff --git a/packages/outline-view/src/browser/outline-view-widget.tsx b/packages/outline-view/src/browser/outline-view-widget.tsx
index f3b6561a90ae8..d197046148ab4 100644
--- a/packages/outline-view/src/browser/outline-view-widget.tsx
+++ b/packages/outline-view/src/browser/outline-view-widget.tsx
@@ -29,7 +29,7 @@ import {
 } from '@theia/core/lib/browser';
 import { OutlineViewTreeModel } from './outline-view-tree-model';
 import { Message } from '@theia/core/shared/@phosphor/messaging';
-import { Emitter, Mutable, UriSelection } from '@theia/core';
+import { Emitter, Is, Mutable, UriSelection } from '@theia/core';
 import * as React from '@theia/core/shared/react';
 import { Range } from '@theia/core/shared/vscode-languageserver-protocol';
 import URI from '@theia/core/lib/common/uri';
@@ -64,7 +64,7 @@ export namespace OutlineSymbolInformationNode {
     }
 
     export function hasRange(node: unknown): node is { range: Range } {
-        return typeof node === 'object' && !!node && 'range' in node && Range.is((node as { range: Range }).range);
+        return Is.object<{ range: Range }>(node) && Range.is(node.range);
     }
 }
 
diff --git a/packages/plugin-ext/src/common/plugin-api-rpc.ts b/packages/plugin-ext/src/common/plugin-api-rpc.ts
index aaaf79f10c844..17fbae988650e 100644
--- a/packages/plugin-ext/src/common/plugin-api-rpc.ts
+++ b/packages/plugin-ext/src/common/plugin-api-rpc.ts
@@ -107,7 +107,7 @@ import type {
 import { SerializableEnvironmentVariableCollection } from '@theia/terminal/lib/common/base-terminal-protocol';
 import { ThemeType } from '@theia/core/lib/common/theme';
 import { Disposable } from '@theia/core/lib/common/disposable';
-import { PickOptions, QuickInputButtonHandle } from '@theia/core/lib/common';
+import { Is, PickOptions, QuickInputButtonHandle } from '@theia/core/lib/common';
 import { Severity } from '@theia/core/lib/common/severity';
 
 export interface PreferenceData {
@@ -776,7 +776,7 @@ export interface TreeViewSelection {
 }
 export namespace TreeViewSelection {
     export function is(arg: unknown): arg is TreeViewSelection {
-        return !!arg && typeof arg === 'object' && 'treeViewId' in arg && 'treeItemId' in arg;
+        return Is.object(arg) && 'treeViewId' in arg && 'treeItemId' in arg;
     }
 }
 
@@ -822,7 +822,7 @@ export interface ScmCommandArg {
 }
 export namespace ScmCommandArg {
     export function is(arg: unknown): arg is ScmCommandArg {
-        return !!arg && typeof arg === 'object' && 'sourceControlHandle' in arg;
+        return Is.object(arg) && 'sourceControlHandle' in arg;
     }
 }
 
@@ -838,7 +838,7 @@ export interface ScmExt {
 
 export namespace TimelineCommandArg {
     export function is(arg: unknown): arg is TimelineCommandArg {
-        return !!arg && typeof arg === 'object' && 'timelineHandle' in arg;
+        return Is.object(arg) && 'timelineHandle' in arg;
     }
 }
 export interface TimelineCommandArg {
@@ -857,7 +857,7 @@ export interface DecorationReply { [id: number]: DecorationData; }
 
 export namespace CommentsCommandArg {
     export function is(arg: unknown): arg is CommentsCommandArg {
-        return !!arg && typeof arg === 'object' && 'commentControlHandle' in arg && 'commentThreadHandle' in arg && 'text' in arg && !('commentUniqueId' in arg);
+        return Is.object(arg) && 'commentControlHandle' in arg && 'commentThreadHandle' in arg && 'text' in arg && !('commentUniqueId' in arg);
     }
 }
 export interface CommentsCommandArg {
@@ -868,7 +868,7 @@ export interface CommentsCommandArg {
 
 export namespace CommentsContextCommandArg {
     export function is(arg: unknown): arg is CommentsContextCommandArg {
-        return !!arg && typeof arg === 'object' && 'commentControlHandle' in arg && 'commentThreadHandle' in arg && 'commentUniqueId' in arg && !('text' in arg);
+        return Is.object(arg) && 'commentControlHandle' in arg && 'commentThreadHandle' in arg && 'commentUniqueId' in arg && !('text' in arg);
     }
 }
 export interface CommentsContextCommandArg {
@@ -879,7 +879,7 @@ export interface CommentsContextCommandArg {
 
 export namespace CommentsEditCommandArg {
     export function is(arg: unknown): arg is CommentsEditCommandArg {
-        return !!arg && typeof arg === 'object' && 'commentControlHandle' in arg && 'commentThreadHandle' in arg && 'commentUniqueId' in arg && 'text' in arg;
+        return Is.object(arg) && 'commentControlHandle' in arg && 'commentThreadHandle' in arg && 'commentUniqueId' in arg && 'text' in arg;
     }
 }
 export interface CommentsEditCommandArg {
diff --git a/packages/plugin-ext/src/common/rpc-protocol.ts b/packages/plugin-ext/src/common/rpc-protocol.ts
index efd5b9503bee3..b9c88e5a91397 100644
--- a/packages/plugin-ext/src/common/rpc-protocol.ts
+++ b/packages/plugin-ext/src/common/rpc-protocol.ts
@@ -30,6 +30,7 @@ import URI from '@theia/core/lib/common/uri';
 import { CancellationToken, CancellationTokenSource } from '@theia/core/shared/vscode-languageserver-protocol';
 import { Range, Position } from '../plugin/types-impl';
 import { BinaryBuffer } from '@theia/core/lib/common/buffer';
+import { Is } from '@theia/core/lib/common/is';
 
 export interface MessageConnection {
     send(msg: string): void;
@@ -71,7 +72,7 @@ export namespace ConnectionClosedError {
         return Object.assign(new Error(message), { code });
     }
     export function is(error: unknown): error is ConnectionClosedError {
-        return !!error && typeof error === 'object' && 'code' in error && (error as ConnectionClosedError).code === code;
+        return Is.object(error) && 'code' in error && (error as ConnectionClosedError).code === code;
     }
 }
 
@@ -469,8 +470,7 @@ enum SerializedObjectType {
 }
 
 function isSerializedObject(obj: unknown): obj is SerializedObject {
-    const serializedObject = obj as SerializedObject;
-    return !!obj && typeof obj === 'object' && serializedObject.$type !== undefined && serializedObject.data !== undefined;
+    return Is.object<SerializedObject>(obj) && obj.$type !== undefined && obj.data !== undefined;
 }
 
 export const enum MessageType {
diff --git a/packages/plugin-ext/src/common/types.ts b/packages/plugin-ext/src/common/types.ts
index d1c8b4c6722f7..20940d637e93b 100644
--- a/packages/plugin-ext/src/common/types.ts
+++ b/packages/plugin-ext/src/common/types.ts
@@ -19,13 +19,13 @@
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/
 
+import { Is } from '@theia/core/lib/common/is';
+
 /**
  * Returns `true` if the parameter has type "object" and not null, an array, a regexp, a date.
  */
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
-export function isObject(obj: any): boolean {
-    return typeof obj === 'object'
-        && obj !== null // eslint-disable-line @typescript-eslint/no-explicit-any
+export function isObject(obj: unknown): boolean {
+    return Is.object(obj)
         && !Array.isArray(obj)
         && !(obj instanceof RegExp)
         && !(obj instanceof Date);
diff --git a/packages/plugin-ext/src/hosted/node/hosted-plugin-localization-service.ts b/packages/plugin-ext/src/hosted/node/hosted-plugin-localization-service.ts
index a3761bdefada3..8531a31a2f05e 100644
--- a/packages/plugin-ext/src/hosted/node/hosted-plugin-localization-service.ts
+++ b/packages/plugin-ext/src/hosted/node/hosted-plugin-localization-service.ts
@@ -23,7 +23,7 @@ import { DeployedPlugin, Localization as PluginLocalization, PluginIdentifiers }
 import { URI } from '@theia/core/shared/vscode-uri';
 import { EnvVariablesServer } from '@theia/core/lib/common/env-variables';
 import { BackendApplicationContribution } from '@theia/core/lib/node';
-import { Disposable } from '@theia/core';
+import { Disposable, Is } from '@theia/core';
 import { Deferred } from '@theia/core/lib/common/promise-util';
 
 export interface VSCodeNlsConfig {
@@ -205,7 +205,7 @@ interface LocalizeInfo {
 }
 
 function isLocalizeInfo(obj: unknown): obj is LocalizeInfo {
-    return typeof obj === 'object' && obj && 'message' in obj || false;
+    return Is.object(obj) && 'message' in obj || false;
 }
 
 function coerceLocalizations(translations: Record<string, string | LocalizeInfo>): Record<string, string> {
@@ -243,7 +243,7 @@ function localizePackage(value: unknown, translations: PackageTranslation, callb
         }
         return result;
     }
-    if (typeof value === 'object' && value) {
+    if (Is.object(value)) {
         const result: Record<string, unknown> = {};
         for (const [name, item] of Object.entries(value)) {
             result[name] = localizePackage(item, translations, callback);
diff --git a/packages/plugin-ext/src/hosted/node/plugin-host.ts b/packages/plugin-ext/src/hosted/node/plugin-host.ts
index fa54f21beb537..645921efe34d1 100644
--- a/packages/plugin-ext/src/hosted/node/plugin-host.ts
+++ b/packages/plugin-ext/src/hosted/node/plugin-host.ts
@@ -14,6 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import '@theia/core/shared/reflect-metadata';
 import { Emitter } from '@theia/core/lib/common/event';
 import { RPCProtocolImpl, MessageType, ConnectionClosedError } from '../../common/rpc-protocol';
 import { PluginHostRPC } from './plugin-host-rpc';
@@ -82,8 +83,7 @@ const rpc = new RPCProtocolImpl({
             process.send(m);
         }
     }
-},
-{
+}, {
     reviver: reviver
 });
 
diff --git a/packages/plugin-ext/src/main/browser/view/tree-view-decorator-service.ts b/packages/plugin-ext/src/main/browser/view/tree-view-decorator-service.ts
index c6df32ad46596..e3840d8277341 100644
--- a/packages/plugin-ext/src/main/browser/view/tree-view-decorator-service.ts
+++ b/packages/plugin-ext/src/main/browser/view/tree-view-decorator-service.ts
@@ -16,9 +16,9 @@
 
 import { inject, injectable, interfaces, named } from '@theia/core/shared/inversify';
 import { AbstractTreeDecoratorService, TreeDecorator } from '@theia/core/lib/browser/tree/tree-decorator';
-import { bindContributionProvider, ContributionProvider } from '@theia/core';
+import { bindContributionProvider, ContributionProvider, Is } from '@theia/core';
 import { TreeNode } from '@theia/core/lib/browser';
-import { TreeItem, Uri } from '@theia/plugin';
+import { TreeItem } from '@theia/plugin';
 import URI from '@theia/core/lib/common/uri';
 import { FileTreeDecoratorAdapter } from '@theia/filesystem/lib/browser';
 
@@ -32,9 +32,8 @@ export class TreeViewDecoratorAdapter extends FileTreeDecoratorAdapter {
         }
     }
 
-    protected isTreeItem(node: unknown): node is TreeItem & { resourceUri: Uri } {
-        const candidate = node as TreeItem;
-        return !!candidate && typeof node === 'object' && 'resourceUri' in candidate && !!candidate.resourceUri;
+    protected isTreeItem(node: unknown): node is TreeItem {
+        return Is.object<TreeItem>(node) && !!node.resourceUri;
     }
 }
 
diff --git a/packages/plugin-ext/src/plugin/languages/code-action.ts b/packages/plugin-ext/src/plugin/languages/code-action.ts
index 5a4729d29cf4e..4ef2a67a25c2b 100644
--- a/packages/plugin-ext/src/plugin/languages/code-action.ts
+++ b/packages/plugin-ext/src/plugin/languages/code-action.ts
@@ -24,6 +24,7 @@ import { Diagnostics } from './diagnostics';
 import { CodeActionKind } from '../types-impl';
 import { CommandRegistryImpl } from '../command-registry';
 import { DisposableCollection } from '@theia/core/lib/common/disposable';
+import { Is } from '@theia/core/lib/common/is';
 
 export class CodeActionAdapter {
 
@@ -147,16 +148,15 @@ export class CodeActionAdapter {
     }
 
     private static _isCommand(arg: unknown): arg is theia.Command {
-        return !!arg && typeof arg === 'object' && typeof (arg as theia.Command).command === 'string';
+        return Is.object<theia.Command>(arg) && typeof arg.command === 'string';
     }
 
-    private static _isSelection(obj: unknown): obj is Selection {
-        const selection = obj as Selection;
-        return !!obj && typeof obj === 'object'
-            && typeof selection.selectionStartLineNumber === 'number'
-            && typeof selection.selectionStartColumn === 'number'
-            && typeof selection.positionLineNumber === 'number'
-            && typeof selection.positionColumn === 'number';
+    private static _isSelection(arg: unknown): arg is Selection {
+        return Is.object<Selection>(arg)
+            && typeof arg.selectionStartLineNumber === 'number'
+            && typeof arg.selectionStartColumn === 'number'
+            && typeof arg.positionLineNumber === 'number'
+            && typeof arg.positionColumn === 'number';
     }
 
 }
diff --git a/packages/plugin-ext/src/plugin/type-converters.ts b/packages/plugin-ext/src/plugin/type-converters.ts
index 9126224e0df44..6105638a7a84e 100644
--- a/packages/plugin-ext/src/plugin/type-converters.ts
+++ b/packages/plugin-ext/src/plugin/type-converters.ts
@@ -28,6 +28,7 @@ import * as types from './types-impl';
 import { UriComponents } from '../common/uri-components';
 import { isReadonlyArray } from '../common/arrays';
 import { MarkdownString as MarkdownStringDTO } from '@theia/core/lib/common/markdown-rendering';
+import { Is } from '@theia/core/lib/common/is';
 
 const SIDE_GROUP = -2;
 const ACTIVE_GROUP = -1;
@@ -138,7 +139,7 @@ export function toPosition(position: Position): types.Position {
 }
 
 function isDecorationOptions(arg: unknown): arg is theia.DecorationOptions {
-    return !!arg && typeof arg === 'object' && typeof (arg as theia.DecorationOptions).range !== 'undefined';
+    return Is.object<theia.DecorationOptions>(arg) && typeof arg.range !== 'undefined';
 }
 
 export function isDecorationOptionsArr(something: theia.Range[] | theia.DecorationOptions[]): something is theia.DecorationOptions[] {
@@ -182,9 +183,9 @@ interface Codeblock {
 }
 
 function isCodeblock(arg: unknown): arg is Codeblock {
-    return !!arg && typeof arg === 'object'
-        && typeof (arg as Codeblock).language === 'string'
-        && typeof (arg as Codeblock).value === 'string';
+    return Is.object<Codeblock>(arg)
+        && typeof arg.language === 'string'
+        && typeof arg.value === 'string';
 }
 
 export function fromMarkdown(markup: theia.MarkdownString | theia.MarkedString): MarkdownStringDTO {
@@ -667,57 +668,47 @@ export function toSymbolTag(kind: model.SymbolTag): types.SymbolTag {
 }
 
 export function isModelLocation(arg: unknown): arg is model.Location {
-    if (!arg) {
-        return false;
-    }
-    return !!arg &&
-        typeof arg === 'object' &&
-        isModelRange((arg as model.Location).range) &&
-        isUriComponents((arg as model.Location).uri);
+    return Is.object<model.Location>(arg) &&
+        isModelRange(arg.range) &&
+        isUriComponents(arg.uri);
 }
 
 export function isModelRange(arg: unknown): arg is model.Range {
-    const range = arg as model.Range;
-    return !!arg && typeof arg === 'object' &&
-        typeof range.startLineNumber === 'number' &&
-        typeof range.startColumn === 'number' &&
-        typeof range.endLineNumber === 'number' &&
-        typeof range.endColumn === 'number';
+    return Is.object<model.Range>(arg) &&
+        typeof arg.startLineNumber === 'number' &&
+        typeof arg.startColumn === 'number' &&
+        typeof arg.endLineNumber === 'number' &&
+        typeof arg.endColumn === 'number';
 }
 
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
 export function isUriComponents(arg: unknown): arg is UriComponents {
-    const uriComponents = arg as UriComponents;
-    return !!arg && typeof arg === 'object' &&
-        typeof uriComponents.scheme === 'string' &&
-        typeof uriComponents.path === 'string' &&
-        typeof uriComponents.query === 'string' &&
-        typeof uriComponents.fragment === 'string';
+    return Is.object<UriComponents>(arg) &&
+        typeof arg.scheme === 'string' &&
+        typeof arg.path === 'string' &&
+        typeof arg.query === 'string' &&
+        typeof arg.fragment === 'string';
 }
 
 export function isModelCallHierarchyItem(arg: unknown): arg is model.CallHierarchyItem {
-    const item = arg as model.CallHierarchyItem;
-    return !!item && typeof item === 'object'
-        && isModelRange(item.range)
-        && isModelRange(item.selectionRange)
-        && isUriComponents(item.uri)
-        && !!item.name;
+    return Is.object<model.CallHierarchyItem>(arg)
+        && isModelRange(arg.range)
+        && isModelRange(arg.selectionRange)
+        && isUriComponents(arg.uri)
+        && !!arg.name;
 }
 
 export function isModelCallHierarchyIncomingCall(arg: unknown): arg is model.CallHierarchyIncomingCall {
-    const maybeIncomingCall = arg as model.CallHierarchyIncomingCall;
-    return !!arg && typeof arg === 'object' &&
-        'from' in maybeIncomingCall &&
-        'fromRanges' in maybeIncomingCall &&
-        isModelCallHierarchyItem(maybeIncomingCall.from);
+    return Is.object<model.CallHierarchyIncomingCall>(arg) &&
+        'from' in arg &&
+        'fromRanges' in arg &&
+        isModelCallHierarchyItem(arg.from);
 }
 
 export function isModelCallHierarchyOutgoingCall(arg: unknown): arg is model.CallHierarchyOutgoingCall {
-    const maybeOutgoingCall = arg as model.CallHierarchyOutgoingCall;
-    return !!arg && typeof arg === 'object' &&
-        'to' in maybeOutgoingCall &&
-        'fromRanges' in maybeOutgoingCall &&
-        isModelCallHierarchyItem(maybeOutgoingCall.to);
+    return Is.object<model.CallHierarchyOutgoingCall>(arg) &&
+        'to' in arg &&
+        'fromRanges' in arg &&
+        isModelCallHierarchyItem(arg.to);
 }
 
 export function toLocation(value: model.Location): types.Location {
@@ -771,12 +762,11 @@ export function toCallHierarchyOutgoingCall(value: model.CallHierarchyOutgoingCa
 }
 
 export function isModelTypeHierarchyItem(arg: unknown): arg is model.TypeHierarchyItem {
-    const item = arg as model.TypeHierarchyItem;
-    return !!item && typeof item === 'object'
-        && isModelRange(item.range)
-        && isModelRange(item.selectionRange)
-        && isUriComponents(item.uri)
-        && !!item.name;
+    return Is.object<model.TypeHierarchyItem>(arg)
+        && isModelRange(arg.range)
+        && isModelRange(arg.selectionRange)
+        && isUriComponents(arg.uri)
+        && !!arg.name;
 }
 
 export function fromTypeHierarchyItem(item: types.TypeHierarchyItem): model.TypeHierarchyItem {
diff --git a/packages/plugin-ext/src/plugin/types-impl.ts b/packages/plugin-ext/src/plugin/types-impl.ts
index b990a737b52e4..b9eb511b987d9 100644
--- a/packages/plugin-ext/src/plugin/types-impl.ts
+++ b/packages/plugin-ext/src/plugin/types-impl.ts
@@ -32,6 +32,7 @@ import { FileSystemProviderErrorCode, markAsFileSystemProviderError } from '@the
 import * as paths from 'path';
 import { ObjectsTransferrer } from '../common/rpc-protocol';
 import { es5ClassCompat } from '../common/types';
+import { Is } from '@theia/core/lib/common/is';
 
 /**
  * A reviver that takes URI's transferred via JSON.stringify() and makes
@@ -546,14 +547,13 @@ export class Range {
         return new Range(start, end);
     }
 
-    static isRange(thing: unknown): thing is theia.Range {
-        if (thing instanceof Range) {
+    static isRange(arg: unknown): arg is theia.Range {
+        if (arg instanceof Range) {
             return true;
         }
-        const range = thing as theia.Range;
-        return !!thing && typeof thing === 'object'
-            && Position.isPosition(range.start)
-            && Position.isPosition(range.end);
+        return Is.object<theia.Range>(arg)
+            && Position.isPosition(arg.start)
+            && Position.isPosition(arg.end);
     }
 
     toJSON(): unknown {
@@ -736,7 +736,7 @@ export class ThemeIcon {
 
 export namespace ThemeIcon {
     export function is(item: unknown): item is ThemeIcon {
-        return typeof item === 'object' && !!item && 'id' in item;
+        return Is.object(item) && 'id' in item;
     }
 }
 
@@ -2784,7 +2784,7 @@ export class SemanticTokensLegend {
 }
 
 function isStrArrayOrUndefined(arg: unknown): arg is string[] | undefined {
-    return ((typeof arg === 'undefined') || (Array.isArray(arg) && arg.every(e => typeof e === 'string')));
+    return typeof arg === 'undefined' || Is.stringArray(arg);
 }
 
 @es5ClassCompat
diff --git a/packages/preferences/src/browser/views/components/preference-file-input.ts b/packages/preferences/src/browser/views/components/preference-file-input.ts
index 4510a1cc26731..19a0cb90fb977 100644
--- a/packages/preferences/src/browser/views/components/preference-file-input.ts
+++ b/packages/preferences/src/browser/views/components/preference-file-input.ts
@@ -14,6 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import { Is } from '@theia/core/lib/common/is';
 import { nls } from '@theia/core/lib/common/nls';
 import { inject, injectable, interfaces } from '@theia/core/shared/inversify';
 import { OpenFileDialogProps } from '@theia/filesystem/lib/browser';
@@ -25,13 +26,13 @@ import { PreferenceLeafNodeRendererContribution } from './preference-node-render
 import { PreferenceStringInputRenderer } from './preference-string-input';
 
 export interface FileNodeTypeDetails {
-    isFilepath: boolean;
+    isFilepath: true;
     selectionProps?: Partial<OpenFileDialogProps>;
 }
 
 export namespace FileNodeTypeDetails {
-    export function is(typeDetails?: unknown): typeDetails is FileNodeTypeDetails {
-        return !!typeDetails && typeof typeDetails === 'object' && !!(typeDetails as FileNodeTypeDetails).isFilepath;
+    export function is(typeDetails: unknown): typeDetails is FileNodeTypeDetails {
+        return Is.object<FileNodeTypeDetails>(typeDetails) && !!typeDetails.isFilepath;
     }
 }
 
diff --git a/packages/preview/src/browser/preview-handler.ts b/packages/preview/src/browser/preview-handler.ts
index f415882e7ee0c..d02a40db7666c 100644
--- a/packages/preview/src/browser/preview-handler.ts
+++ b/packages/preview/src/browser/preview-handler.ts
@@ -16,7 +16,7 @@
 
 import { inject, injectable, named } from '@theia/core/shared/inversify';
 import URI from '@theia/core/lib/common/uri';
-import { ContributionProvider, MaybePromise, Prioritizeable } from '@theia/core';
+import { ContributionProvider, Is, MaybePromise, Prioritizeable } from '@theia/core';
 
 export const PreviewHandler = Symbol('PreviewHandler');
 
@@ -36,7 +36,7 @@ export interface RenderContentParams {
 
 export namespace RenderContentParams {
     export function is(params: unknown): params is RenderContentParams {
-        return !!params && typeof params === 'object' && 'content' in params && 'originUri' in params;
+        return Is.object(params) && 'content' in params && 'originUri' in params;
     }
 }
 
diff --git a/packages/process/src/node/process.ts b/packages/process/src/node/process.ts
index a234d11864e77..c1cf3db29736a 100644
--- a/packages/process/src/node/process.ts
+++ b/packages/process/src/node/process.ts
@@ -16,7 +16,7 @@
 
 import { injectable, unmanaged } from '@theia/core/shared/inversify';
 import { ProcessManager } from './process-manager';
-import { ILogger, Emitter, Event } from '@theia/core/lib/common';
+import { ILogger, Emitter, Event, Is } from '@theia/core/lib/common';
 import { FileUri } from '@theia/core/lib/node';
 import { isOSX, isWindows } from '@theia/core';
 import { Readable, Writable } from 'stream';
@@ -193,7 +193,7 @@ export abstract class Process {
     }
 
     protected isForkOptions(options: unknown): options is ForkOptions {
-        return !!options && typeof options === 'object' && !!(options as ForkOptions).modulePath;
+        return Is.object<ForkOptions>(options) && !!options.modulePath;
     }
 
     protected readonly initialCwd: string;
diff --git a/packages/scm-extra/src/browser/history/scm-history-widget.tsx b/packages/scm-extra/src/browser/history/scm-history-widget.tsx
index 6bae5883a8218..0df75af4a0c71 100644
--- a/packages/scm-extra/src/browser/history/scm-history-widget.tsx
+++ b/packages/scm-extra/src/browser/history/scm-history-widget.tsx
@@ -15,7 +15,7 @@
 // *****************************************************************************
 
 import { injectable, inject, postConstruct } from '@theia/core/shared/inversify';
-import { Event as TheiaEvent, DisposableCollection } from '@theia/core';
+import { Event as TheiaEvent, DisposableCollection, Is } from '@theia/core';
 import { OpenerService, open, StatefulWidget, SELECTED_CLASS, WidgetManager, ApplicationShell, codicon } from '@theia/core/lib/browser';
 import { CancellationTokenSource } from '@theia/core/lib/common/cancellation';
 import { Message } from '@theia/core/shared/@phosphor/messaging';
@@ -48,7 +48,7 @@ export interface ScmCommitNode {
 
 export namespace ScmCommitNode {
     export function is(node: unknown): node is ScmCommitNode {
-        return !!node && typeof node === 'object' && 'commitDetails' in node && 'expanded' in node && 'selected' in node;
+        return Is.object(node) && 'commitDetails' in node && 'expanded' in node && 'selected' in node;
     }
 }
 
diff --git a/packages/scm-extra/src/browser/scm-file-change-node.ts b/packages/scm-extra/src/browser/scm-file-change-node.ts
index a42d7b393e0aa..f9607fc261ca0 100644
--- a/packages/scm-extra/src/browser/scm-file-change-node.ts
+++ b/packages/scm-extra/src/browser/scm-file-change-node.ts
@@ -16,6 +16,7 @@
 
 import { ScmCommit } from '@theia/scm/lib/browser/scm-provider';
 import URI from '@theia/core/lib/common/uri';
+import { Is } from '@theia/core/lib/common/is';
 
 export interface ScmFileChangeNode {
     readonly fileChange: ScmFileChange;
@@ -24,7 +25,7 @@ export interface ScmFileChangeNode {
 }
 export namespace ScmFileChangeNode {
     export function is(node: unknown): node is ScmFileChangeNode {
-        return !!node && typeof node === 'object' && 'fileChange' in node && 'commitId' in node;
+        return Is.object(node) && 'fileChange' in node && 'commitId' in node;
     }
 }
 
diff --git a/packages/task/src/browser/task-configuration-model.ts b/packages/task/src/browser/task-configuration-model.ts
index e9814fb3080df..f63e5b23e2c12 100644
--- a/packages/task/src/browser/task-configuration-model.ts
+++ b/packages/task/src/browser/task-configuration-model.ts
@@ -19,6 +19,7 @@ import { Emitter, Event } from '@theia/core/lib/common/event';
 import { Disposable, DisposableCollection } from '@theia/core/lib/common/disposable';
 import { TaskCustomization, TaskConfiguration, TaskConfigurationScope } from '../common/task-protocol';
 import { PreferenceProvider, PreferenceProviderDataChanges, PreferenceProviderDataChange } from '@theia/core/lib/browser';
+import { Is } from '@theia/core/lib/common/is';
 
 /**
  * Holds the task configurations associated with a particular file. Uses an editor model to facilitate
@@ -80,11 +81,9 @@ export class TaskConfigurationModel implements Disposable {
         const configurations: (TaskCustomization | TaskConfiguration)[] = [];
         // eslint-disable-next-line @typescript-eslint/no-explicit-any
         const { configUri, value } = this.preferences.resolve<any>('tasks', this.getWorkspaceFolder());
-        if (value && typeof value === 'object' && 'tasks' in value) {
-            if (Array.isArray(value.tasks)) {
-                for (const taskConfig of value.tasks) {
-                    configurations.push(taskConfig);
-                }
+        if (Is.object(value) && Array.isArray(value.tasks)) {
+            for (const taskConfig of value.tasks) {
+                configurations.push(taskConfig);
             }
         }
         return {
diff --git a/packages/toolbar/src/browser/toolbar-constants.ts b/packages/toolbar/src/browser/toolbar-constants.ts
index 507b53250c7b5..38deac3e8b914 100644
--- a/packages/toolbar/src/browser/toolbar-constants.ts
+++ b/packages/toolbar/src/browser/toolbar-constants.ts
@@ -14,7 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
-import { Command, MenuPath, nls } from '@theia/core';
+import { Command, Is, MenuPath, nls } from '@theia/core';
 import { CommonCommands } from '@theia/core/lib/browser';
 import URI from '@theia/core/lib/common/uri';
 import { UserStorageUri } from '@theia/userstorage/lib/browser';
@@ -74,6 +74,6 @@ export namespace ToolbarMenus {
 export type ReactInteraction<T = Element, U = MouseEvent> = React.MouseEvent<T, U> | React.KeyboardEvent<T>;
 export namespace ReactKeyboardEvent {
     export function is(obj: unknown): obj is React.KeyboardEvent {
-        return typeof obj === 'object' && !!obj && 'key' in obj;
+        return Is.object(obj) && 'key' in obj;
     }
 }
diff --git a/packages/workspace/src/browser/workspace-schema-updater.ts b/packages/workspace/src/browser/workspace-schema-updater.ts
index 8556243d92372..7e585177a06d3 100644
--- a/packages/workspace/src/browser/workspace-schema-updater.ts
+++ b/packages/workspace/src/browser/workspace-schema-updater.ts
@@ -16,7 +16,7 @@
 
 import { inject, injectable, postConstruct } from '@theia/core/shared/inversify';
 import { JsonSchemaContribution, JsonSchemaRegisterContext } from '@theia/core/lib/browser/json-schema-store';
-import { InMemoryResources } from '@theia/core/lib/common';
+import { InMemoryResources, Is } from '@theia/core/lib/common';
 import { IJSONSchema } from '@theia/core/lib/common/json-schema';
 import URI from '@theia/core/lib/common/uri';
 import { Deferred } from '@theia/core/lib/common/promise-util';
@@ -114,12 +114,11 @@ export class WorkspaceSchemaUpdater implements JsonSchemaContribution {
 export type WorkspaceSchema = Required<Pick<IJSONSchema, 'properties' | 'required'>>;
 
 export namespace WorkspaceSchema {
-    export const is = (candidate: unknown): candidate is WorkspaceSchema => !!candidate
-        && typeof candidate === 'object'
-        && 'properties' in candidate
-        && typeof (candidate as WorkspaceSchema).properties === 'object'
-        && 'required' in candidate
-        && Array.isArray((candidate as WorkspaceSchema).required);
+    export function is(candidate: unknown): candidate is WorkspaceSchema {
+        return Is.object<WorkspaceSchema>(candidate)
+            && typeof candidate.properties === 'object'
+            && Array.isArray(candidate.required);
+    }
 }
 
 export const workspaceSchemaId = 'vscode://schemas/workspace';