diff --git a/README.md b/README.md
index 5503c93..73df45c 100644
--- a/README.md
+++ b/README.md
@@ -42,7 +42,9 @@ Install aria2.js
 npm install aria2
 ```
 
-then
+[↑](#aria2js)
+
+## Usage
 
 ```js
 import Aria2 from "aria2";
@@ -52,9 +54,7 @@ const aria2 = new Aria2(options);
 
 In the browser you can also use `node_modules/aria2/bundle.js` directly in `<script>` and `window.Aria2`.
 
-[↑](#aria2js)
-
-## Usage
+Aria2 extends [EventTarget](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget).
 
 Default options match aria2c defaults and are
 
@@ -81,10 +81,8 @@ The `"aria2."` prefix can be omitted from both methods and notifications.
 `aria2.open()` opens the WebSocket connection. All subsequent requests will use the WebSocket transport instead of HTTP.
 
 ```javascript
-aria2
-  .open()
-  .then(() => console.log("open"))
-  .catch((err) => console.log("error", err));
+await aria2.open();
+console.log("open");
 ```
 
 [↑](#aria2js)
@@ -94,10 +92,8 @@ aria2
 `aria2.close()` closes the WebSocket connection. All subsequent requests will use the HTTP transport instead of WebSocket.
 
 ```javascript
-aria2
-  .close()
-  .then(() => console.log("closed"))
-  .catch((err) => console.log("error", err));
+await aria2.close();
+console.log("closed");
 ```
 
 [↑](#aria2js)
@@ -111,7 +107,7 @@ Example using [`addUri`](https://aria2.github.io/manual/en/html/aria2c.html#aria
 ```javascript
 const magnet =
   "magnet:?xt=urn:btih:88594AAACBDE40EF3E2510C47374EC0AA396C08E&dn=bbb_sunflower_1080p_30fps_normal.mp4&tr=udp%3a%2f%2ftracker.openbittorrent.com%3a80%2fannounce&tr=udp%3a%2f%2ftracker.publicbt.com%3a80%2fannounce&ws=http%3a%2f%2fdistribution.bbb3d.renderfarming.net%2fvideo%2fmp4%2fbbb_sunflower_1080p_30fps_normal.mp4";
-const [guid] = await aria2.call("addUri", [magnet], { dir: "/tmp" });
+const guid = await aria2.call("addUri", [magnet], { dir: "/tmp" });
 ```
 
 [↑](#aria2js)
@@ -163,9 +159,9 @@ const notifications = await aria2.listNotifications();
 
 // notifications logger example
 notifications.forEach((notification) => {
-  aria2.on(notification, (params) => {
-    console.log("aria2", notification, params);
-  });
+  aria2.addEventListener(notification, ({detail}) => {
+    console.log("aria2", notification, detail);
+  }});
 });
 ```
 
@@ -191,30 +187,37 @@ const methods = await aria2.listMethods();
 
 ```javascript
 // emitted when the WebSocket is open.
-aria2.on("open", () => {
-  console.log("aria2 OPEN");
+aria2.addEventListener("open", () => {
+  console.log("aria2", "OPEN");
 });
 
 // emitted when the WebSocket is closed.
-aria2.on("close", () => {
-  console.log("aria2 CLOSE");
+aria2.addEventListener("close", () => {
+  console.log("aria2", "CLOSE");
+});
+
+// emitted when error occur.
+aria2.addEventListener("error", ({ error }) => {
+  console.error("aria2", "error", error);
 });
 
-// emitted for every message sent.
-aria2.on("output", (m) => {
-  console.log("aria2 OUT", m);
+// emitted for every data sent.
+aria2.addEventListener("input", ({ data }) => {
+  console.log("aria2", "IN");
+  console.dir(data);
 });
 
-// emitted for every message received.
-aria2.on("input", (m) => {
-  console.log("aria2 IN", m);
+// emitted for every data received.
+aria2.addEventListener("output", ({ data }) => {
+  console.log("aria2", "OUT");
+  console.dir(data);
 });
 ```
 
-Additionally every [aria2 notifications](https://aria2.github.io/manual/en/html/aria2c.html#notifications) received will be emitted as an event (with and without the `"aria2."` prefix). Only available when using WebSocket, see [open](#open).
+Additionally, every [aria2 notifications](https://aria2.github.io/manual/en/html/aria2c.html#notifications) received will be emitted as an event (with and without the `"aria2."` prefix). Only available when using WebSocket, see [open](#open).
 
 ```javascript
-aria2.on("onDownloadStart", ([guid]) => {
+aria2.addEventListener("onDownloadStart", ({detail: [guid]}) => {
   console.log("aria2 onDownloadStart", guid);
 });
 ```
diff --git a/example.js b/example.js
new file mode 100644
index 0000000..f1cff70
--- /dev/null
+++ b/example.js
@@ -0,0 +1,25 @@
+import Aria2 from "./src/Aria2.js"; // or "aria2" if installed with npm
+import debug from "./src/debug.js";
+
+(async () => {
+  const aria2 = new Aria2();
+  debug(aria2);
+
+  // comment to use HTTP
+  try {
+    await aria2.open();
+  } catch (err) {
+    console.log("Could not connect");
+    return;
+  }
+
+  aria2.addEventListener("onDownloadStart", ({ detail }) => {
+    console.log("Download start", detail);
+  });
+
+  const magnet =
+    "magnet:?xt=urn:btih:88594AAACBDE40EF3E2510C47374EC0AA396C08E&dn=bbb_sunflower_1080p_30fps_normal.mp4&tr=udp%3a%2f%2ftracker.openbittorrent.com%3a80%2fannounce&tr=udp%3a%2f%2ftracker.publicbt.com%3a80%2fannounce&ws=http%3a%2f%2fdistribution.bbb3d.renderfarming.net%2fvideo%2fmp4%2fbbb_sunflower_1080p_30fps_normal.mp4";
+  const guid = await aria2.call("addUri", [magnet], { dir: "/tmp" });
+
+  console.log("guid", guid);
+})();
diff --git a/package-lock.json b/package-lock.json
index 9f6c03f..8421e29 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -15,7 +15,7 @@
         "rollup-plugin-polyfill-node": "^0.13.0"
       },
       "engines": {
-        "node": ">= 20.10.0"
+        "node": ">= 22.0.0"
       }
     },
     "node_modules/@isaacs/cliui": {
diff --git a/package.json b/package.json
index 295a3c6..8dbc2cd 100644
--- a/package.json
+++ b/package.json
@@ -1,13 +1,12 @@
 {
   "name": "aria2",
-  "version": "4.1.2",
+  "version": "5.0.0",
   "description": "Library and for aria2, \"The next generation download utility.\"",
   "homepage": "https://github.com/sonnyp/aria2.js",
   "bugs": "https://github.com/sonnyp/aria2.js/issues",
   "license": "ISC",
   "type": "module",
-  "main": "./cjs/Aria2.js",
-  "module": "./src/Aria2.js",
+  "main": "./src/Aria2.js",
   "author": "Sonny Piers <sonny@fastmail.net>",
   "keywords": [
     "aria2",
diff --git a/rollup.config.js b/rollup.config.js
index 970af79..b3ab409 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -1,15 +1,6 @@
 import nodePolyfills from "rollup-plugin-polyfill-node";
 
 export default [
-  {
-    input: ["src/Aria2.js"],
-    output: {
-      dir: "cjs",
-      format: "cjs",
-      preserveModules: true,
-      exports: "auto",
-    },
-  },
   {
     input: "src/Aria2.js",
     output: {
@@ -17,6 +8,7 @@ export default [
       format: "iife",
       name: "Aria2",
     },
+    // Still needed?
     plugins: [nodePolyfills()],
   },
 ];
diff --git a/src/Aria2.js b/src/Aria2.js
index e7bd929..d093490 100644
--- a/src/Aria2.js
+++ b/src/Aria2.js
@@ -1,4 +1,4 @@
-import JSONRPCClient from "./JSONRPCClient.js";
+import JSONRPCClient, { JSONRPCNotificationEvent } from "./JSONRPCClient.js";
 
 function prefix(str) {
   if (!str.startsWith("system.") && !str.startsWith("aria2.")) {
@@ -24,7 +24,8 @@ class Aria2 extends JSONRPCClient {
   _onnotification(notification) {
     const { method, params } = notification;
     const event = unprefix(method);
-    if (event !== method) this.emit(event, params);
+    if (event !== method)
+      this.dispatchEvent(new JSONRPCNotificationEvent(event, { params }));
     return super._onnotification(notification);
   }
 
diff --git a/src/JSONRPCClient.js b/src/JSONRPCClient.js
index 420a456..163cd34 100644
--- a/src/JSONRPCClient.js
+++ b/src/JSONRPCClient.js
@@ -1,20 +1,37 @@
-import { EventEmitter } from "events";
-
 import promiseEvent from "./promiseEvent.js";
 import JSONRPCError from "./JSONRPCError.js";
 
-class JSONRPCClient extends EventEmitter {
+// https://github.com/nodejs/node/issues/58918
+if (!globalThis.ErrorEvent) {
+  globalThis.ErrorEvent = class ErrorEvent extends Event {
+    constructor(type, options) {
+      super(type, options);
+      this.error = options?.error;
+    }
+  };
+}
+
+export class JSONRPCEvent extends Event {
+  constructor(type, options) {
+    super(type, options);
+    this.data = options?.data;
+  }
+}
+
+export class JSONRPCNotificationEvent extends Event {
+  constructor(type, options) {
+    super(type, options);
+    this.params = options?.params;
+  }
+}
+
+class JSONRPCClient extends EventTarget {
   constructor(options) {
     super();
     this.deferreds = Object.create(null);
     this.lastId = 0;
 
-    Object.assign(
-      this,
-      { WebSocket: global.WebSocket, fetch: global.fetch.bind(this) },
-      this.constructor.defaultOptions,
-      options,
-    );
+    Object.assign(this, this.constructor.defaultOptions, options);
   }
 
   id() {
@@ -33,19 +50,12 @@ class JSONRPCClient extends EventEmitter {
     );
   }
 
-  websocket(message) {
-    return new Promise((resolve, reject) => {
-      const cb = (err) => {
-        if (err) reject(err);
-        else resolve();
-      };
-      this.socket.send(JSON.stringify(message), cb);
-      if (global.WebSocket && this.socket instanceof global.WebSocket) cb();
-    });
+  async websocket(message) {
+    this.socket.send(JSON.stringify(message));
   }
 
   async http(message) {
-    const response = await this.fetch(this.url("http"), {
+    const response = await fetch(this.url("http"), {
       method: "POST",
       body: JSON.stringify(message),
       headers: {
@@ -54,14 +64,16 @@ class JSONRPCClient extends EventEmitter {
       },
     });
 
-    response
-      .json()
-      .then((msg) => this._onmessage(msg))
-      .catch((err) => {
-        this.emit("error", err);
-      });
+    let msg;
+    try {
+      msg = await response.json();
+      this._onmessage(msg);
+    } catch (error) {
+      this.dispatchEvent(new ErrorEvent("error", { error }));
+      throw error;
+    }
 
-    return response;
+    return msg;
   }
 
   _buildMessage(method, params) {
@@ -80,8 +92,6 @@ class JSONRPCClient extends EventEmitter {
   }
 
   async batch(calls) {
-    const promises = [];
-
     const message = calls.map(([method, params]) => {
       return this._buildMessage(method, params);
     });
@@ -104,7 +114,7 @@ class JSONRPCClient extends EventEmitter {
   }
 
   async _send(message) {
-    this.emit("output", message);
+    this.dispatchEvent(new JSONRPCEvent("output", { data: message }));
 
     const { socket } = this;
     return socket && socket.readyState === 1
@@ -125,11 +135,11 @@ class JSONRPCClient extends EventEmitter {
   }
 
   _onnotification({ method, params }) {
-    this.emit(method, params);
+    this.dispatchEvent(new JSONRPCNotificationEvent(method, { params }));
   }
 
   _onmessage(message) {
-    this.emit("input", message);
+    this.dispatchEvent(new JSONRPCEvent("input", { data: message }));
 
     if (Array.isArray(message)) {
       for (const object of message) {
@@ -147,26 +157,26 @@ class JSONRPCClient extends EventEmitter {
   }
 
   async open() {
-    const socket = (this.socket = new this.WebSocket(this.url("ws")));
+    const socket = (this.socket = new WebSocket(this.url("ws")));
 
-    socket.onclose = (...args) => {
-      this.emit("close", ...args);
+    socket.onclose = (evt) => {
+      this.dispatchEvent(new Event("close"));
     };
     socket.onmessage = (event) => {
       let message;
       try {
         message = JSON.parse(event.data);
-      } catch (err) {
-        this.emit("error", err);
+      } catch (error) {
+        this.dispatchEvent(new ErrorEvent("error", { error }));
         return;
       }
       this._onmessage(message);
     };
-    socket.onopen = (...args) => {
-      this.emit("open", ...args);
+    socket.onopen = (evt) => {
+      this.dispatchEvent(new Event("open"));
     };
-    socket.onerror = (...args) => {
-      this.emit("error", ...args);
+    socket.onerror = (evt) => {
+      this.dispatchEvent(new ErrorEvent("error", { error: evt }));
     };
 
     return promiseEvent(this, "open");
diff --git a/src/debug.js b/src/debug.js
index 09dcafd..a3ef962 100644
--- a/src/debug.js
+++ b/src/debug.js
@@ -1,21 +1,28 @@
-import { inspect } from "util";
-
 export default function (aria2) {
-  aria2.on("open", () => {
+  // emitted when the WebSocket is open.
+  aria2.addEventListener("open", () => {
     console.log("aria2", "OPEN");
   });
 
-  aria2.on("close", () => {
+  // emitted when the WebSocket is closed.
+  aria2.addEventListener("close", () => {
     console.log("aria2", "CLOSE");
   });
 
-  aria2.on("input", (m) => {
+  // emitted when error occur.
+  aria2.addEventListener("error", ({ error }) => {
+    console.error("aria2", "error", error);
+  });
+
+  // emitted for every data sent.
+  aria2.addEventListener("input", ({ data }) => {
     console.log("aria2", "IN");
-    console.log(inspect(m, { depth: null, colors: true }));
+    console.dir(data);
   });
 
-  aria2.on("output", (m) => {
+  // emitted for every data received.
+  aria2.addEventListener("output", ({ data }) => {
     console.log("aria2", "OUT");
-    console.log(inspect(m, { depth: null, colors: true }));
+    console.dir(data);
   });
 }
diff --git a/src/promiseEvent.js b/src/promiseEvent.js
index 8ad7944..726db31 100644
--- a/src/promiseEvent.js
+++ b/src/promiseEvent.js
@@ -1,8 +1,8 @@
 export default function promiseEvent(target, event) {
   return new Promise((resolve, reject) => {
     function cleanup() {
-      target.removeListener(event, onEvent);
-      target.removeListener("error", onError);
+      target.removeEventListener(event, onEvent);
+      target.removeEventListener("error", onError);
     }
     function onEvent(data) {
       resolve(data);
@@ -12,7 +12,7 @@ export default function promiseEvent(target, event) {
       reject(err);
       cleanup();
     }
-    target.addListener(event, onEvent);
-    target.addListener("error", onError);
+    target.addEventListener(event, onEvent);
+    target.addEventListener("error", onError);
   });
 }
diff --git a/test/Aria2.js b/test/Aria2.js
index 5289b94..01ac9e2 100644
--- a/test/Aria2.js
+++ b/test/Aria2.js
@@ -1,7 +1,7 @@
 import test from "ava";
+import promiseEvent from "../src/promiseEvent.js";
 
 import Aria2 from "../src/Aria2.js";
-import promiseEvent from "../src/promiseEvent.js";
 
 Object.assign(global, { fetch, WebSocket });
 
@@ -113,5 +113,5 @@ test("#_onnotification", async (t) => {
   const promise = promiseEvent(aria2, "onDownloadStart");
   aria2._onnotification({ method: "aria2.onDownloadStart", params });
 
-  t.is(await promise, params);
+  t.is((await promise).params, params);
 });
diff --git a/test/JSONRPCClient.js b/test/JSONRPCClient.js
index 35d45be..4a21fd8 100644
--- a/test/JSONRPCClient.js
+++ b/test/JSONRPCClient.js
@@ -1,6 +1,7 @@
-import { once } from "node:events";
 import test from "ava";
+import { mock } from "node:test";
 
+import promiseEvent from "../src/promiseEvent.js";
 import JSONRPCClient from "../src/JSONRPCClient.js";
 
 Object.assign(global, { fetch, WebSocket });
@@ -35,9 +36,8 @@ test("#websocket", async (t) => {
   const message = { hello: "world" };
 
   client.socket = {
-    send(str, cb) {
+    async send(str) {
       t.is(str, JSON.stringify(message));
-      cb();
     },
   };
 
@@ -52,9 +52,9 @@ test("#websocket error", async (t) => {
   const error = new Error();
 
   client.socket = {
-    send(str, cb) {
+    send(str) {
       t.is(str, JSON.stringify(message));
-      cb(error);
+      throw error;
     },
   };
 
@@ -74,13 +74,13 @@ test("#websocket json error", async (t) => {
   client.open();
   client.socket.onopen();
 
-  const promise_error = once(client, "error");
+  const promise_error = promiseEvent(client, "error");
 
   try {
     client.socket.onmessage({ data: "foo" });
   } catch {}
 
-  const [error] = await promise_error;
+  const { error } = await promise_error;
   t.true(error instanceof SyntaxError);
   t.is(error.message, `Unexpected token 'o', "foo" is not valid JSON`);
 });
@@ -92,7 +92,8 @@ test("#http", async (t) => {
   const request = { hello: "world" };
   const response = { world: "hello" };
 
-  client.fetch = (url, options) => {
+  const fetch = globalThis.fetch;
+  globalThis.fetch = (url, options) => {
     t.is(url, "http://localhost:80/jsonrpc");
     t.deepEqual(options, {
       method: "POST",
@@ -114,12 +115,15 @@ test("#http", async (t) => {
   };
 
   client.http(request);
+
+  globalThis.fetch = fetch;
 });
 
 test("#http fetch error", async (t) => {
   const client = new JSONRPCClient();
 
-  client.fetch = () => Promise.reject(new Error("foo"));
+  const fetch = globalThis.fetch;
+  globalThis.fetch = () => Promise.reject(new Error("foo"));
 
   await t.throwsAsync(
     async () => {
@@ -127,25 +131,41 @@ test("#http fetch error", async (t) => {
     },
     { message: "foo" },
   );
+  globalThis.fetch = fetch;
 });
 
 test("#http json error", async (t) => {
+  t.plan(2);
+
   const client = new JSONRPCClient();
 
-  client.fetch = () => {
+  let err;
+
+  const fetch = globalThis.fetch;
+  globalThis.fetch = () => {
     return Promise.resolve({
-      async json() {
-        return JSON.parse("foo");
-      },
+      json: mock.fn(async () => {
+        try {
+          JSON.parse("foo");
+        } catch (error) {
+          err = error;
+          throw err;
+        }
+      }),
     });
   };
 
-  client.on("error", (err) => {
-    t.true(err instanceof SyntaxError);
-    t.is(err.message, `Unexpected token 'o', "foo" is not valid JSON`);
+  client.addEventListener("error", ({ error }) => {
+    t.is(error.message, err.message);
   });
 
-  await client.http({});
+  try {
+    await client.http({});
+  } catch (error) {
+    t.is(error.message, err.message);
+  }
+
+  globalThis.fetch = fetch;
 });
 
 test("#_buildMessage", (t) => {
@@ -231,7 +251,7 @@ test("#send", async (t) => {
 
   const message = {};
 
-  client.on("output", (m) => {
+  client.addEventListener("output", ({ data: m }) => {
     t.is(m, message);
   });