diff --git a/README.md b/README.md
index 2ab8263..3c91ed1 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,10 @@ React Hook designed to provide robust WebSocket integrations to your React Compo
 
 Pull requests welcomed!
 
+## ESM-only package
+
+Starting with this version, `react-use-websocket` is published as ESM-only. Use `import` syntax when consuming the package. CommonJS `require('react-use-websocket')` is not supported.
+
 ## New in 4.0.0
 
 - `react-use-websocket` now supports (and depends on) React 18. If you are not ready to upgrade to React 18, please install version `3.0.0`:
diff --git a/package.json b/package.json
index babf933..6d269ce 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,14 @@
   "name": "react-use-websocket",
   "version": "4.13.0",
   "description": "React Hook for WebSocket communication",
+  "type": "module",
   "main": "./dist/index.js",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    }
+  },
   "files": [
     "src",
     "dist"
@@ -10,7 +17,7 @@
   "scripts": {
     "test": "cross-env node_modules/.bin/jest --verbose --no-cache",
     "clear-dist": "cross-env rm -rf dist/",
-    "compile": "cross-env node_modules/.bin/tsc -p .",
+    "compile": "cross-env node_modules/.bin/tsc -p tsconfig.build.json",
     "push": "cross-env npm run test && npm run clear-dist && npm run compile && npm publish"
   },
   "repository": {
@@ -42,15 +49,28 @@
     "typescript": "^5.6.2"
   },
   "jest": {
-    "preset": "ts-jest",
+    "preset": "ts-jest/presets/default-esm",
     "clearMocks": true,
     "coverageDirectory": "coverage",
     "testEnvironment": "jsdom",
+    "extensionsToTreatAsEsm": [
+      ".ts",
+      ".tsx"
+    ],
     "testMatch": [
       "<rootDir>/src/lib/**/*.test.(ts|tsx)"
     ],
     "transform": {
-      "^.+\\.(ts|tsx)?$": "ts-jest"
+      "^.+\\.(ts|tsx)?$": [
+        "ts-jest",
+        {
+          "useESM": true,
+          "tsconfig": "tsconfig.test.json"
+        }
+      ]
+    },
+    "moduleNameMapper": {
+      "^(\\.{1,2}/.*)\\.js$": "$1"
     },
     "setupFiles": [
       "./__test__/configJSDom.ts"
diff --git a/src/index.ts b/src/index.ts
index 5c09663..d62b117 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,11 +1,11 @@
-export { useWebSocket as default } from './lib/use-websocket';
+export { useWebSocket as default } from './lib/use-websocket.js';
 
-export { SendMessage, Options } from './lib/types';
+export { SendMessage, Options } from './lib/types.js';
 
-export { useSocketIO } from './lib/use-socket-io';
+export { useSocketIO } from './lib/use-socket-io.js';
 
-export { ReadyState } from './lib/constants';
+export { ReadyState } from './lib/constants.js';
 
-export { useEventSource } from './lib/use-event-source';
+export { useEventSource } from './lib/use-event-source.js';
 
-export { resetGlobalState } from './lib/util';
+export { resetGlobalState } from './lib/util.js';
diff --git a/src/lib/attach-listener.test.ts b/src/lib/attach-listener.test.ts
index aeab13e..1718661 100644
--- a/src/lib/attach-listener.test.ts
+++ b/src/lib/attach-listener.test.ts
@@ -1,8 +1,8 @@
 import { MutableRefObject } from 'react';
-import { attachListeners } from './attach-listener';
+import { attachListeners } from './attach-listener.js';
 import WS from "jest-websocket-mock";
-import { Options } from './types';
-import { ReadyState } from './constants';
+import { Options } from './types.js';
+import { ReadyState } from './constants.js';
 
 let server: WS;
 
diff --git a/src/lib/attach-listener.ts b/src/lib/attach-listener.ts
index d660d3b..d297e60 100644
--- a/src/lib/attach-listener.ts
+++ b/src/lib/attach-listener.ts
@@ -1,14 +1,14 @@
 import { MutableRefObject } from 'react';
-import { setUpSocketIOPing } from './socket-io';
-import { heartbeat } from './heartbeat';
+import { setUpSocketIOPing } from './socket-io.js';
+import { heartbeat } from './heartbeat.js';
 import {
   DEFAULT_RECONNECT_LIMIT,
   DEFAULT_RECONNECT_INTERVAL_MS,
   ReadyState,
   isEventSourceSupported,
-} from './constants';
-import { Options, SendMessage, WebSocketLike } from './types';
-import { assertIsWebSocket } from './util';
+} from './constants.js';
+import { Options, SendMessage, WebSocketLike } from './types.js';
+import { assertIsWebSocket } from './util.js';
 
 export interface Setters {
   setLastMessage: (message: WebSocketEventMap['message']) => void;
diff --git a/src/lib/attach-shared-listeners.test.ts b/src/lib/attach-shared-listeners.test.ts
index 0a3b36e..038be33 100644
--- a/src/lib/attach-shared-listeners.test.ts
+++ b/src/lib/attach-shared-listeners.test.ts
@@ -1,10 +1,10 @@
 import { MutableRefObject } from 'react';
-import { attachSharedListeners } from './attach-shared-listeners';
+import { attachSharedListeners } from './attach-shared-listeners.js';
 import WS from "jest-websocket-mock";
-import { Options, Subscriber } from './types';
-import { ReadyState } from './constants';
-import { sharedWebSockets } from './globals';
-import { addSubscriber, removeSubscriber, getSubscribers, hasSubscribers } from './manage-subscribers';
+import { Options, Subscriber } from './types.js';
+import { ReadyState } from './constants.js';
+import { sharedWebSockets } from './globals.js';
+import { addSubscriber, removeSubscriber, getSubscribers, hasSubscribers } from './manage-subscribers.js';
 
 let server: WS;
 const URL = 'ws://localhost:1234';
diff --git a/src/lib/attach-shared-listeners.ts b/src/lib/attach-shared-listeners.ts
index 48d2420..761210c 100644
--- a/src/lib/attach-shared-listeners.ts
+++ b/src/lib/attach-shared-listeners.ts
@@ -1,10 +1,10 @@
-import { sharedWebSockets } from './globals';
-import { DEFAULT_RECONNECT_LIMIT, DEFAULT_RECONNECT_INTERVAL_MS, ReadyState, isEventSourceSupported } from './constants';
-import { getSubscribers } from './manage-subscribers';
+import { sharedWebSockets } from './globals.js';
+import { DEFAULT_RECONNECT_LIMIT, DEFAULT_RECONNECT_INTERVAL_MS, ReadyState, isEventSourceSupported } from './constants.js';
+import { getSubscribers } from './manage-subscribers.js';
 import { MutableRefObject } from 'react';
-import { HeartbeatOptions, Options, SendMessage, WebSocketLike } from './types';
-import { setUpSocketIOPing } from './socket-io';
-import { heartbeat } from './heartbeat';
+import { HeartbeatOptions, Options, SendMessage, WebSocketLike } from './types.js';
+import { setUpSocketIOPing } from './socket-io.js';
+import { heartbeat } from './heartbeat.js';
 
 const bindMessageHandler = (
   webSocketInstance: WebSocketLike,
diff --git a/src/lib/constants.ts b/src/lib/constants.ts
index 301caba..15f10b3 100644
--- a/src/lib/constants.ts
+++ b/src/lib/constants.ts
@@ -1,4 +1,4 @@
-import { EventSourceEventHandlers, EventSourceOptions } from "./types";
+import { EventSourceEventHandlers, EventSourceOptions } from "./types.js";
 
 const MILLISECONDS = 1;
 const SECONDS = 1000 * MILLISECONDS;
diff --git a/src/lib/create-or-join.test.ts b/src/lib/create-or-join.test.ts
index c31b8de..5024793 100644
--- a/src/lib/create-or-join.test.ts
+++ b/src/lib/create-or-join.test.ts
@@ -1,8 +1,8 @@
 import { MutableRefObject } from 'react';
-import { createOrJoinSocket } from './create-or-join';
+import { createOrJoinSocket } from './create-or-join.js';
 import WS from "jest-websocket-mock";
-import { Options } from './types';
-import { removeSubscriber, getSubscribers, hasSubscribers } from './manage-subscribers';
+import { Options } from './types.js';
+import { removeSubscriber, getSubscribers, hasSubscribers } from './manage-subscribers.js';
 
 let server: WS;
 const URL = 'ws://localhost:1234';
diff --git a/src/lib/create-or-join.ts b/src/lib/create-or-join.ts
index f22a57b..9fdf4fd 100644
--- a/src/lib/create-or-join.ts
+++ b/src/lib/create-or-join.ts
@@ -1,10 +1,10 @@
 import { MutableRefObject } from 'react';
-import { sharedWebSockets } from './globals';
-import { Options, SendMessage, Subscriber, WebSocketLike } from './types';
-import { isEventSourceSupported, ReadyState, isReactNative } from './constants';
-import { attachListeners } from './attach-listener';
-import { attachSharedListeners } from './attach-shared-listeners';
-import { addSubscriber, removeSubscriber, hasSubscribers } from './manage-subscribers';
+import { sharedWebSockets } from './globals.js';
+import { Options, SendMessage, Subscriber, WebSocketLike } from './types.js';
+import { isEventSourceSupported, ReadyState, isReactNative } from './constants.js';
+import { attachListeners } from './attach-listener.js';
+import { attachSharedListeners } from './attach-shared-listeners.js';
+import { addSubscriber, removeSubscriber, hasSubscribers } from './manage-subscribers.js';
 
 //TODO ensure that all onClose callbacks are called
 
diff --git a/src/lib/get-url.test.ts b/src/lib/get-url.test.ts
index 43c8ced..c0ff27b 100644
--- a/src/lib/get-url.test.ts
+++ b/src/lib/get-url.test.ts
@@ -1,6 +1,6 @@
 import { MutableRefObject } from 'react';
-import { getUrl } from './get-url';
-import { Options } from './types';
+import { getUrl } from './get-url.js';
+import { Options } from './types.js';
 
 let optionRef: MutableRefObject<Options>;
 
diff --git a/src/lib/get-url.ts b/src/lib/get-url.ts
index fe1e911..404fd5d 100644
--- a/src/lib/get-url.ts
+++ b/src/lib/get-url.ts
@@ -1,7 +1,7 @@
 import { MutableRefObject } from 'react';
-import { parseSocketIOUrl, appendQueryParams } from './socket-io';
-import { Options } from './types';
-import { DEFAULT_RECONNECT_INTERVAL_MS, DEFAULT_RECONNECT_LIMIT } from './constants';
+import { parseSocketIOUrl, appendQueryParams } from './socket-io.js';
+import { Options } from './types.js';
+import { DEFAULT_RECONNECT_INTERVAL_MS, DEFAULT_RECONNECT_LIMIT } from './constants.js';
 
 const waitFor = (duration: number) => new Promise(resolve => window.setTimeout(resolve, duration));
 
diff --git a/src/lib/globals.test.ts b/src/lib/globals.test.ts
index 934aebc..28cb48d 100644
--- a/src/lib/globals.test.ts
+++ b/src/lib/globals.test.ts
@@ -1,5 +1,5 @@
-import { sharedWebSockets, resetWebSockets } from './globals';
-import { WebSocketLike } from './types';
+import { sharedWebSockets, resetWebSockets } from './globals.js';
+import { WebSocketLike } from './types.js';
 
 const FIRST_URL = 'ws://localhost:1234';
 const SECOND_URL = 'ws://localhost:4321';
diff --git a/src/lib/globals.ts b/src/lib/globals.ts
index 6ed6c11..2c5e1ca 100644
--- a/src/lib/globals.ts
+++ b/src/lib/globals.ts
@@ -1,4 +1,4 @@
-import { WebSocketLike } from "./types";
+import { WebSocketLike } from "./types.js";
 
 export interface SharedWebSockets {
   [url: string]: WebSocketLike;
diff --git a/src/lib/heartbeat.test.ts b/src/lib/heartbeat.test.ts
index 4afc644..dcac140 100644
--- a/src/lib/heartbeat.test.ts
+++ b/src/lib/heartbeat.test.ts
@@ -1,4 +1,4 @@
-import { heartbeat } from "./heartbeat";
+import { heartbeat } from "./heartbeat.js";
 
 describe("heartbeat", () => {
   let ws: WebSocket;
diff --git a/src/lib/heartbeat.ts b/src/lib/heartbeat.ts
index 0b6bc48..b7dc4c3 100644
--- a/src/lib/heartbeat.ts
+++ b/src/lib/heartbeat.ts
@@ -1,6 +1,6 @@
 import { MutableRefObject } from "react";
-import { DEFAULT_HEARTBEAT } from "./constants";
-import { HeartbeatOptions } from "./types";
+import { DEFAULT_HEARTBEAT } from "./constants.js";
+import { HeartbeatOptions } from "./types.js";
 
 function getLastMessageTime(lastMessageTime: MutableRefObject<number> | MutableRefObject<number>[]): number {
   if (Array.isArray(lastMessageTime)) {
diff --git a/src/lib/manage-subscribers.test.ts b/src/lib/manage-subscribers.test.ts
index ea9ee33..5f0e42c 100644
--- a/src/lib/manage-subscribers.test.ts
+++ b/src/lib/manage-subscribers.test.ts
@@ -4,8 +4,8 @@ import {
     addSubscriber,
     removeSubscriber,
     resetSubscribers,
-} from './manage-subscribers';
-import { Subscriber } from './types';
+} from './manage-subscribers.js';
+import { Subscriber } from './types.js';
 
 const URL = 'ws://localhost:1234';
 const SECOND_URL = 'ws://localhost:4321'
diff --git a/src/lib/manage-subscribers.ts b/src/lib/manage-subscribers.ts
index 473b2f3..acc153b 100644
--- a/src/lib/manage-subscribers.ts
+++ b/src/lib/manage-subscribers.ts
@@ -1,4 +1,4 @@
-import { Subscriber } from './types';
+import { Subscriber } from './types.js';
 
 export type Subscribers = {
     [url: string]: Set<Subscriber>,
diff --git a/src/lib/proxy.test.ts b/src/lib/proxy.test.ts
index beb0432..1e3e839 100644
--- a/src/lib/proxy.test.ts
+++ b/src/lib/proxy.test.ts
@@ -1,4 +1,4 @@
-import { websocketWrapper } from './proxy';
+import { websocketWrapper } from './proxy.js';
 import WS from "jest-websocket-mock";
 
 let server: WS;
diff --git a/src/lib/socket-io.test.ts b/src/lib/socket-io.test.ts
index 0388d48..cfc35aa 100644
--- a/src/lib/socket-io.test.ts
+++ b/src/lib/socket-io.test.ts
@@ -2,8 +2,8 @@ import {
   parseSocketIOUrl,
   appendQueryParams,
   setUpSocketIOPing,
-} from './socket-io';
-import { SOCKET_IO_PING_CODE } from './constants';
+} from './socket-io.js';
+import { SOCKET_IO_PING_CODE } from './constants.js';
 import WS from "jest-websocket-mock";
 
 let server: WS;
diff --git a/src/lib/socket-io.ts b/src/lib/socket-io.ts
index fcffc6f..cfd6a71 100644
--- a/src/lib/socket-io.ts
+++ b/src/lib/socket-io.ts
@@ -1,5 +1,5 @@
-import { SOCKET_IO_PING_INTERVAL, SOCKET_IO_PATH, SOCKET_IO_PING_CODE } from './constants';
-import { QueryParams, SendMessage } from './types';
+import { SOCKET_IO_PING_INTERVAL, SOCKET_IO_PATH, SOCKET_IO_PING_CODE } from './constants.js';
+import { QueryParams, SendMessage } from './types.js';
 
 export const parseSocketIOUrl = (url: string) => {
   if (url) {
diff --git a/src/lib/types.ts b/src/lib/types.ts
index 2d9423f..b3fd15e 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -1,5 +1,5 @@
 import { MutableRefObject } from 'react';
-import { ReadyState } from './constants';
+import { ReadyState } from './constants.js';
 
 export interface QueryParams {
   [key: string]: string | number;
diff --git a/src/lib/use-event-source.test.ts b/src/lib/use-event-source.test.ts
index d1cf4f7..f136aac 100644
--- a/src/lib/use-event-source.test.ts
+++ b/src/lib/use-event-source.test.ts
@@ -1,8 +1,8 @@
 import { renderHook, waitFor } from '@testing-library/react';
-import { useEventSource } from './use-event-source';
+import { useEventSource } from './use-event-source.js';
 import WS from "jest-websocket-mock";
-import { EventSourceOptions } from './types';
-import { DEFAULT_EVENT_SOURCE_OPTIONS } from './constants';
+import { EventSourceOptions } from './types.js';
+import { DEFAULT_EVENT_SOURCE_OPTIONS } from './constants.js';
 
 let server: WS;
 const URL = 'ws://localhost:1234';
diff --git a/src/lib/use-event-source.ts b/src/lib/use-event-source.ts
index aa54179..b0a3857 100644
--- a/src/lib/use-event-source.ts
+++ b/src/lib/use-event-source.ts
@@ -1,7 +1,7 @@
 import { useEffect, useRef } from 'react'
-import { useWebSocket } from './use-websocket'
-import { DEFAULT_EVENT_SOURCE_OPTIONS, EMPTY_EVENT_HANDLERS } from './constants'
-import { EventSourceOptions, Options, EventSourceHook, EventSourceEventHandlers } from './types';
+import { useWebSocket } from './use-websocket.js'
+import { DEFAULT_EVENT_SOURCE_OPTIONS, EMPTY_EVENT_HANDLERS } from './constants.js'
+import { EventSourceOptions, Options, EventSourceHook, EventSourceEventHandlers } from './types.js';
 
 export const useEventSource = (
   url: string | (() => string | Promise<string>) | null,
diff --git a/src/lib/use-socket-io.ts b/src/lib/use-socket-io.ts
index 20227dc..346208f 100644
--- a/src/lib/use-socket-io.ts
+++ b/src/lib/use-socket-io.ts
@@ -1,7 +1,7 @@
 import { useMemo } from 'react'
-import { useWebSocket } from './use-websocket'
-import { DEFAULT_OPTIONS } from './constants'
-import { Options, WebSocketHook } from './types';
+import { useWebSocket } from './use-websocket.js'
+import { DEFAULT_OPTIONS } from './constants.js'
+import { Options, WebSocketHook } from './types.js';
 
 export interface SocketIOMessageData<T = unknown> {
   type: string,
diff --git a/src/lib/use-websocket.test.ts b/src/lib/use-websocket.test.ts
index 90ea64b..6e67f7f 100644
--- a/src/lib/use-websocket.test.ts
+++ b/src/lib/use-websocket.test.ts
@@ -1,9 +1,9 @@
 import { renderHook, waitFor } from '@testing-library/react';
-import { useWebSocket } from './use-websocket';
+import { useWebSocket } from './use-websocket.js';
 import WS from "jest-websocket-mock";
-import { Options } from './types';
-import { ReadyState } from './constants';
-import { parseSocketIOUrl } from './socket-io';
+import { Options } from './types.js';
+import { ReadyState } from './constants.js';
+import { parseSocketIOUrl } from './socket-io.js';
 
 let server: WS;
 const URL = 'ws://localhost:1234';
diff --git a/src/lib/use-websocket.ts b/src/lib/use-websocket.ts
index 82f60e5..bc07b2d 100644
--- a/src/lib/use-websocket.ts
+++ b/src/lib/use-websocket.ts
@@ -1,9 +1,9 @@
 import { useEffect, useRef, useState, useCallback, useMemo } from 'react';
 import { flushSync } from 'react-dom';
-import { DEFAULT_OPTIONS, isEventSourceSupported, ReadyState, UNPARSABLE_JSON_OBJECT } from './constants';
-import { createOrJoinSocket } from './create-or-join';
-import { getUrl } from './get-url';
-import websocketWrapper from './proxy';
+import { DEFAULT_OPTIONS, isEventSourceSupported, ReadyState, UNPARSABLE_JSON_OBJECT } from './constants.js';
+import { createOrJoinSocket } from './create-or-join.js';
+import { getUrl } from './get-url.js';
+import websocketWrapper from './proxy.js';
 import {
   Options,
   ReadyStateState,
@@ -12,8 +12,8 @@ import {
   WebSocketMessage,
   WebSocketHook,
   WebSocketLike,
-} from './types';
-import { assertIsWebSocket } from './util';
+} from './types.js';
+import { assertIsWebSocket } from './util.js';
 
 export const useWebSocket = <T = unknown>(
   url: string | (() => string | Promise<string>) | null,
diff --git a/src/lib/util.ts b/src/lib/util.ts
index 1ab29a1..1ed8336 100644
--- a/src/lib/util.ts
+++ b/src/lib/util.ts
@@ -1,6 +1,6 @@
-import { WebSocketLike } from './types';
-import { resetWebSockets } from './globals';
-import { resetSubscribers } from './manage-subscribers';
+import { WebSocketLike } from './types.js';
+import { resetWebSockets } from './globals.js';
+import { resetSubscribers } from './manage-subscribers.js';
 
 export function assertIsWebSocket (
     webSocketInstance: WebSocketLike,
diff --git a/tsconfig.base.json b/tsconfig.base.json
new file mode 100644
index 0000000..b681bd2
--- /dev/null
+++ b/tsconfig.base.json
@@ -0,0 +1,27 @@
+{
+  "compilerOptions": {
+    "sourceMap": true,
+    "esModuleInterop": true,
+    "target": "es5",
+    "jsx": "react",
+    "skipLibCheck": true,
+    "lib": [
+      "es2017",
+      "dom"
+    ],
+    "strict": true,
+    "declaration": true,
+    "baseUrl": ".",
+    "paths": {
+      "@lib/*": [
+        "src/lib/*"
+      ]
+    }
+  },
+  "files": [
+    "./src/index.ts"
+  ],
+  "include": [
+    "src/*"
+  ]
+}
diff --git a/tsconfig.build.json b/tsconfig.build.json
new file mode 100644
index 0000000..f77319c
--- /dev/null
+++ b/tsconfig.build.json
@@ -0,0 +1,12 @@
+{
+  "extends": "./tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "./dist/",
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "types": [
+      "node",
+      "websocket"
+    ]
+  }
+}
diff --git a/tsconfig.json b/tsconfig.json
index 90c8ebf..452f262 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,27 +1,3 @@
 {
-  "compilerOptions": {
-      "outDir": "./dist/",
-      "sourceMap": true,
-      "module": "commonjs",
-      "esModuleInterop": true,
-      "target": "es5",
-      "jsx": "react",
-      "skipLibCheck": true,
-      "lib": ["es2017", "dom"],
-      "types" : ["node", "websocket", "jest"],
-      "strict": true,
-      "declaration": true,
-      "baseUrl": ".",
-      "paths": {
-        "@lib/*": [
-            "src/lib/*"
-        ]
-    }
-  },
-  "files": [
-    "./src/index.ts"
-  ],
-  "include": [
-    "src/*"
-  ]
+  "extends": "./tsconfig.test.json"
 }
diff --git a/tsconfig.test.json b/tsconfig.test.json
new file mode 100644
index 0000000..5a3fb0e
--- /dev/null
+++ b/tsconfig.test.json
@@ -0,0 +1,13 @@
+{
+  "extends": "./tsconfig.base.json",
+  "compilerOptions": {
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "types": [
+      "node",
+      "websocket",
+      "jest"
+    ],
+    "noEmit": true
+  }
+}