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Matrix JavaScript SDK

This is the Matrix Client-Server SDK for JavaScript and TypeScript. This SDK can be run in a browser or in Node.js.

The Matrix specification is constantly evolving - while this SDK aims for maximum backwards compatibility, it only guarantees that a feature will be supported for at least 4 spec releases. For example, if a feature the js-sdk supports is removed in v1.4 then the feature is eligible for removal from the SDK when v1.8 is released. This SDK has no guarantee on implementing all features of any particular spec release, currently. This can mean that the SDK will call endpoints from before Matrix 1.1, for example.


In a browser

Download the browser version from and add that as a <script> to your page. There will be a global variable matrixcs attached to window through which you can access the SDK. See below for how to include libolm to enable end-to-end-encryption.

The browser bundle supports recent versions of browsers. Typically this is ES2015 or > 0.5%, last 2 versions, Firefox ESR, not dead if using browserlists.

Please check the working browser example for more information.

In Node.js

Ensure you have the latest LTS version of Node.js installed. This library relies on fetch which is available in Node from v18.0.0 - it should work fine also with polyfills. If you wish to use a ponyfill or adapter of some sort then pass it as fetchFn to the MatrixClient constructor options.

Using yarn instead of npm is recommended. Please see the Yarn install guide if you do not have it already.

yarn add matrix-js-sdk

import * as sdk from "matrix-js-sdk";
const client = sdk.createClient({ baseUrl: "" });
client.publicRooms(function (err, data) {
    console.log("Public Rooms: %s", JSON.stringify(data));

See below for how to include libolm to enable end-to-end-encryption. Please check the Node.js terminal app for a more complex example.

To start the client:

await client.startClient({ initialSyncLimit: 10 });

You can perform a call to /sync to get the current state of the client:

client.once("sync", function (state, prevState, res) {
    if (state === "PREPARED") {
    } else {

To send a message:

const content = {
    body: "message text",
    msgtype: "m.text",
client.sendEvent("roomId", "", content, "", (err, res) => {

To listen for message events:

client.on("Room.timeline", function (event, room, toStartOfTimeline) {
    if (event.getType() !== "") {
        return; // only use messages

By default, the matrix-js-sdk client uses the MemoryStore to store events as they are received. For example to iterate through the currently stored timeline for a room:

Object.keys( => {
    client.getRoom(roomId).timeline.forEach((t) => {

What does this SDK do?

This SDK provides a full object model around the Matrix Client-Server API and emits events for incoming data and state changes. Aside from wrapping the HTTP API, it:

  • Handles syncing (via /initialSync and /events)
  • Handles the generation of "friendly" room and member names.
  • Handles historical RoomMember information (e.g. display names).
  • Manages room member state across multiple events (e.g. it handles typing, power levels and membership changes).
  • Exposes high-level objects like Rooms, RoomState, RoomMembers and Users which can be listened to for things like name changes, new messages, membership changes, presence changes, and more.
  • Handle "local echo" of messages sent using the SDK. This means that messages that have just been sent will appear in the timeline as 'sending', until it completes. This is beneficial because it prevents there being a gap between hitting the send button and having the "remote echo" arrive.
  • Mark messages which failed to send as not sent.
  • Automatically retry requests to send messages due to network errors.
  • Automatically retry requests to send messages due to rate limiting errors.
  • Handle queueing of messages.
  • Handles pagination.
  • Handle assigning push actions for events.
  • Handles room initial sync on accepting invites.
  • Handles WebRTC calling.

Later versions of the SDK will:

  • Expose a RoomSummary which would be suitable for a recents page.
  • Provide different pluggable storage layers (e.g. local storage, database-backed)



Emitted events

The SDK will emit events using an EventEmitter. It also emits object models (e.g. Rooms, RoomMembers) when they are updated.

// Listen for low-level MatrixEvents
client.on("event", function (event) {

// Listen for typing changes
client.on("RoomMember.typing", function (event, member) {
    if (member.typing) {
        console.log( + " is typing...");
    } else {
        console.log( + " stopped typing.");

// start the client to setup the connection to the server

Promises and Callbacks

Most of the methods in the SDK are asynchronous: they do not directly return a result, but instead return a Promise which will be fulfilled in the future.

The typical usage is something like:

  matrixClient.someMethod(arg1, arg2).then(function(result) {

Alternatively, if you have a Node.js-style callback(err, result) function, you can pass the result of the promise into it with something like:

matrixClient.someMethod(arg1, arg2).nodeify(callback);

The main thing to note is that it is problematic to discard the result of a promise-returning function, as that will cause exceptions to go unobserved.

Methods which return a promise show this in their documentation.

Many methods in the SDK support both Node.js-style callbacks and Promises, via an optional callback argument. The callback support is now deprecated: new methods do not include a callback argument, and in the future it may be removed from existing methods.


This section provides some useful code snippets which demonstrate the core functionality of the SDK. These examples assume the SDK is setup like this:

import * as sdk from "matrix-js-sdk";
const myUserId = "@example:localhost";
const myAccessToken = "QGV4YW1wbGU6bG9jYWxob3N0.qPEvLuYfNBjxikiCjP";
const matrixClient = sdk.createClient({
    baseUrl: "http://localhost:8008",
    accessToken: myAccessToken,
    userId: myUserId,

Automatically join rooms when invited

matrixClient.on("RoomMember.membership", function (event, member) {
    if (member.membership === "invite" && member.userId === myUserId) {
        matrixClient.joinRoom(member.roomId).then(function () {
            console.log("Auto-joined %s", member.roomId);


Print out messages for all rooms

matrixClient.on("Room.timeline", function (event, room, toStartOfTimeline) {
    if (toStartOfTimeline) {
        return; // don't print paginated results
    if (event.getType() !== "") {
        return; // only print messages
        // the room name will update with events automatically
        "(%s) %s :: %s",,



  (My Room) @megan:localhost :: Hello world
  (My Room) @megan:localhost :: how are you?
  (My Room) @example:localhost :: I am good
  (My Room) @example:localhost :: change the room name
  (My New Room) @megan:localhost :: done

Print out membership lists whenever they are changed

matrixClient.on("RoomState.members", function (event, state, member) {
    const room = matrixClient.getRoom(state.roomId);
    if (!room) {
    const memberList = state.getMembers();
    console.log(Array( + 1).join("=")); // underline
    for (var i = 0; i < memberList.length; i++) {
        console.log("(%s) %s", memberList[i].membership, memberList[i].name);



  My Room
  (join) @example:localhost
  (leave) @alice:localhost
  (join) Bob
  (invite) @charlie:localhost

API Reference

A hosted reference can be found at

This SDK uses Typedoc doc comments. You can manually build and host the API reference from the source files like this:

  $ yarn gendoc
  $ cd _docs
  $ python -m http.server 8005

Then visit http://localhost:8005 to see the API docs.

End-to-end encryption support

The SDK supports end-to-end encryption via the Olm and Megolm protocols, using libolm. It is left up to the application to make libolm available, via the Olm global.

It is also necessary to call await matrixClient.initCrypto() after creating a new MatrixClient (but before calling matrixClient.startClient()) to initialise the crypto layer.

If the Olm global is not available, the SDK will show a warning, as shown below; initCrypto() will also fail.

Unable to load crypto module: crypto will be disabled: Error: global.Olm is not defined

If the crypto layer is not (successfully) initialised, the SDK will continue to work for unencrypted rooms, but it will not support the E2E parts of the Matrix specification.

To provide the Olm library in a browser application:

To provide the Olm library in a node.js application:

  • yarn add (replace the URL with the latest version you want to use from
  • global.Olm = require('olm'); before loading matrix-js-sdk.

If you want to package Olm as dependency for your node.js application, you can use yarn add If your application also works without e2e crypto enabled, add --optional to mark it as an optional dependency.


This section is for people who want to modify the SDK. If you just want to use this SDK, skip this section.

First, you need to pull in the right build tools:

 $ yarn install


To build a browser version from scratch when developing::

 $ yarn build

To run tests (Jest):

 $ yarn test

Note The sync-browserify.spec.ts requires a browser build (yarn build) in order to pass

To run linting:

 $ yarn lint



npm i matrix-js-sdk-bastyon

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