diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..b3a5643
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,57 @@
+import { pki } from 'node-forge'
+
+declare interface SelfsignedOptions {
+  /**
+   * The number of days before expiration
+   *
+   * @default 365 */
+  days?: number
+  /**
+   * the size for the private key in bits
+   * @default 1024
+   */
+  keySize?: number
+  /**
+   * additional extensions for the certificate
+   */
+  extensions?: string[]
+  /**
+   * The signature algorithm sha256 or sha1
+   * @default "sha1"
+   */
+  algorithm?: string
+  /**
+   * include PKCS#7 as part of the output
+   * @default false
+   */
+  pkcs7?: boolean
+  /**
+   * generate client cert signed by the original key
+   * @default false
+   */
+  clientCertificate?: undefined
+  /**
+   * client certificate's common name
+   * @default "John Doe jdoe123"
+   */
+  clientCertificateCN?: string
+}
+
+declare interface GenerateResult {
+  private: string
+  public: string
+  cert: string
+  fingerprint: string
+}
+
+declare function generate(
+  attrs?: pki.CertificateField[],
+  opts?: SelfsignedOptions
+): GenerateResult
+
+declare function generate(
+  attrs?: pki.CertificateField[],
+  opts?: SelfsignedOptions,
+  /** Optional callback, if not provided the generation is synchronous */
+  done?: (err: undefined | Error, result: GenerateResult) => any
+): void
diff --git a/package.json b/package.json
index 4feade7..e6af953 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,7 @@
   "version": "2.0.1",
   "description": "Generate self signed certificates private and public keys",
   "main": "index.js",
+  "types": "index.d.ts",
   "scripts": {
     "test": "mocha -t 5000"
   },