diff --git a/src/browser_action/index.css b/src/browser_action/index.css
index 7a58ec9..c281d34 100644
--- a/src/browser_action/index.css
+++ b/src/browser_action/index.css
@@ -21,8 +21,10 @@ body {
 }
 
 #browser-action-app {
-  min-width: 320px;
-  max-width: 400px; /* Overflow menu popup width exceeds 320px and cannot be changed */
+  width: 320px;
+}
+
+#browser-action-app.overflow {
   width: 100%;
 }
 
diff --git a/src/browser_action/index.jsx b/src/browser_action/index.jsx
index 57dc807..6253e29 100644
--- a/src/browser_action/index.jsx
+++ b/src/browser_action/index.jsx
@@ -20,6 +20,12 @@ if (extractedProductJSON) {
   appProps.extractedProduct = JSON.parse(extractedProductJSON);
 }
 
+(async function checkOverflow() {
+  if (await browser.customizableUI.isWidgetInOverflow('shopping-testpilot_mozilla_org-browser-action')) {
+    document.getElementById('browser-action-app').classList.add('overflow');
+  }
+}());
+
 ReactDOM.render(
   <Provider store={store}>
     <BrowserActionApp {...appProps} />
diff --git a/src/experiment_apis/customizableUI/api.js b/src/experiment_apis/customizableUI/api.js
index 1af7a8b..50f6159 100644
--- a/src/experiment_apis/customizableUI/api.js
+++ b/src/experiment_apis/customizableUI/api.js
@@ -5,6 +5,7 @@
 
 this.customizableUI = class extends ExtensionAPI {
   getAPI(context) {
+    const {Services} = ChromeUtils.import('resource://gre/modules/Services.jsm');
     ChromeUtils.import('resource://gre/modules/ExtensionCommon.jsm');
     const {EventManager} = ExtensionCommon;
     const {CustomizableUI} = ChromeUtils.import('resource:///modules/CustomizableUI.jsm', {});
@@ -25,6 +26,10 @@ this.customizableUI = class extends ExtensionAPI {
             };
           },
         ).api(),
+        async isWidgetInOverflow(widgetId) {
+          const browserWindow = Services.wm.getMostRecentWindow('navigator:browser');
+          return CustomizableUI.getWidget(widgetId).forWindow(browserWindow).overflowed;
+        },
       },
     };
   }
diff --git a/src/experiment_apis/customizableUI/schema.json b/src/experiment_apis/customizableUI/schema.json
index d177a40..6179b04 100644
--- a/src/experiment_apis/customizableUI/schema.json
+++ b/src/experiment_apis/customizableUI/schema.json
@@ -14,6 +14,21 @@
           }
         ]
       }
+    ],
+    "functions": [
+      {
+        "name": "isWidgetInOverflow",
+        "type": "function",
+        "description": "Returns a boolean for whether or not the provided widget in the provided window is in the overflow menu or not.",
+        "async": true,
+        "parameters": [
+          {
+            "name": "widgetId",
+            "type": "string",
+            "description": "The id of the widget to check."
+          }
+        ]
+      }
     ]
   }
 ]