diff --git a/.eslintignore b/.eslintignore
index 44edcd6..1adec14 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -1,3 +1,4 @@
 fixtures
 coverage
 playground
+*.d.ts
diff --git a/.gitignore b/.gitignore
index ccb6dcf..c0263b1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,4 @@ node_modules
 coverage
 playground
 *.tgz
+package-lock.json
diff --git a/fetch.d.ts b/fetch.d.ts
new file mode 100644
index 0000000..f0dd38a
--- /dev/null
+++ b/fetch.d.ts
@@ -0,0 +1,40 @@
+// Type definitions for fetch.js
+
+/**
+ * Options for fetchRecorder
+ */
+export interface FetchRecorderOptions {
+  /**
+   * Base fetch implementation to use. Defaults to globalThis.fetch
+   */
+  fetch?: typeof fetch
+}
+
+/**
+ * Creates a fetch implementation that records all requests to a log array
+ * @param log - Array to append request/response logs to
+ * @param options - Optional configuration
+ * @returns A fetch function that records requests
+ */
+export function fetchRecorder(
+  log: any[],
+  options?: FetchRecorderOptions
+): typeof fetch
+
+/**
+ * Creates a fetch implementation that replays requests from a log array
+ * @param log - Array of recorded request/response logs
+ * @returns A fetch function that replays recorded requests
+ */
+export function fetchReplayer(log: any[]): typeof fetch
+
+/**
+ * Creates a custom fetch implementation using a lookup function
+ * @param lookup - Function to lookup request/response data
+ * @param fallback - Optional fallback fetch function
+ * @returns A fetch function
+ */
+export function fetchApi(
+  lookup: (resource: RequestInfo | URL, options?: RequestInit) => Promise<any>,
+  fallback?: typeof fetch
+): typeof fetch
diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..10ed925
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,16 @@
+// Re-export types and functions from individual modules
+export type { FetchRecorderOptions } from './fetch.js'
+
+export { fetchRecorder, fetchReplayer, fetchApi } from './fetch.js'
+
+export type {
+  WebSocketRecorderOptions,
+  WebSocketReplayerOptions,
+} from './websocket.js'
+
+export { WebSocketRecorder, WebSocketReplayer } from './websocket.js'
+
+export type { PrettyJSONOptions } from './util.js'
+
+export { prettyJSON } from './util.js'
+
diff --git a/package.json b/package.json
index 78677d2..ec30794 100644
--- a/package.json
+++ b/package.json
@@ -21,16 +21,30 @@
   "license": "MIT",
   "type": "module",
   "main": "./index.js",
+  "types": "./index.d.ts",
   "exports": {
-    ".": "./index.js",
-    "./fetch": "./fetch.js",
-    "./websocket": "./websocket.js"
+    ".": {
+      "types": "./index.d.ts",
+      "default": "./index.js"
+    },
+    "./fetch": {
+      "types": "./fetch.d.ts",
+      "default": "./fetch.js"
+    },
+    "./websocket": {
+      "types": "./websocket.d.ts",
+      "default": "./websocket.js"
+    }
   },
   "files": [
     "fetch.js",
+    "fetch.d.ts",
     "index.js",
+    "index.d.ts",
     "util.js",
+    "util.d.ts",
     "websocket.js",
+    "websocket.d.ts",
     "CHANGELOG.md"
   ],
   "scripts": {
diff --git a/util.d.ts b/util.d.ts
new file mode 100644
index 0000000..416f21e
--- /dev/null
+++ b/util.d.ts
@@ -0,0 +1,20 @@
+// Type definitions for util.js
+
+/**
+ * Options for prettyJSON formatting
+ */
+export interface PrettyJSONOptions {
+  /**
+   * Maximum width for inline formatting. Default: 120
+   */
+  width?: number
+}
+
+/**
+ * Pretty-prints JSON data for human-readable logs
+ * @param data - Data to format
+ * @param options - Formatting options
+ * @returns Pretty-printed JSON string
+ */
+export function prettyJSON(data: any, options?: PrettyJSONOptions): string
+
diff --git a/websocket.d.ts b/websocket.d.ts
new file mode 100644
index 0000000..4bcfb34
--- /dev/null
+++ b/websocket.d.ts
@@ -0,0 +1,46 @@
+// Type definitions for websocket.js
+
+/**
+ * Options for WebSocketRecorder
+ */
+export interface WebSocketRecorderOptions {
+  /**
+   * Base WebSocket implementation to use. Defaults to globalThis.WebSocket
+   */
+  WebSocket?: typeof WebSocket
+}
+
+/**
+ * Creates a WebSocket class that records all sessions to a log array
+ * @param log - Array to append session logs to
+ * @param options - Optional configuration
+ * @returns A WebSocket class that records sessions
+ */
+export function WebSocketRecorder(
+  log: any[],
+  options?: WebSocketRecorderOptions
+): typeof WebSocket
+
+/**
+ * Options for WebSocketReplayer
+ */
+export interface WebSocketReplayerOptions {
+  /**
+   * Delay interval for replaying events
+   * - 0: immediate (default)
+   * - Infinity: match original timing
+   * - number: maximum delay between events
+   */
+  interval?: number
+}
+
+/**
+ * Creates a WebSocket class that replays sessions from a log array
+ * @param log - Array of recorded session logs
+ * @param options - Optional configuration
+ * @returns A WebSocket class that replays recorded sessions
+ */
+export function WebSocketReplayer(
+  log: any[],
+  options?: WebSocketReplayerOptions
+): typeof WebSocket