Element

Element (formerly known as Vector and Riot) is a Matrix web client built using the Matrix React SDK.

Supported Environments

Element has several tiers of support for different environments:

• Supported
  • Definition: Issues actively triaged, regressions block the release
  • Last 2 major versions of Chrome, Firefox, and Edge on desktop OSes
  • Last 2 versions of Safari
  • Latest release of official Element Desktop app on desktop OSes
  • Desktop OSes means macOS, Windows, and Linux versions for desktop devices that are actively supported by the OS vendor and receive security updates
• Experimental
  • Definition: Issues accepted, regressions do not block the release
  • Element as an installed PWA via current stable version of Chrome
  • Mobile web for current stable version of Chrome, Firefox, and Safari on Android, iOS, and iPadOS
• Not supported
  • Definition: Issues only affecting unsupported environments are closed
  • Everything else

For accessing Element on an Android or iOS device, we currently recommend the native apps element-android and element-ios.

Getting Started

The easiest way to test Element is to just use the hosted copy at https://app.element.io. The develop branch is continuously deployed to https://develop.element.io for those who like living dangerously.

To host your own instance of Element see Installing Element Web.

To install Element as a desktop application, see Running as a desktop app below.

Important Security Notes

Separate domains

We do not recommend running Element from the same domain name as your Matrix homeserver. The reason is the risk of XSS (cross-site-scripting) vulnerabilities that could occur if someone caused Element to load and render malicious user generated content from a Matrix API which then had trusted access to Element (or other apps) due to sharing the same domain.

We have put some coarse mitigations into place to try to protect against this situation, but it's still not good practice to do it in the first place. See https://github.com/element-hq/element-web/issues/1977 for more details.

Configuration best practices

Unless you have special requirements, you will want to add the following to your web server configuration when hosting Element Web:

• The X-Frame-Options: SAMEORIGIN header, to prevent Element Web from being framed and protect from clickjacking.
• The frame-ancestors 'self' directive to your Content-Security-Policy header, as the modern replacement for X-Frame-Options (though both should be included since not all browsers support it yet, see this).
• The X-Content-Type-Options: nosniff header, to disable MIME sniffing.
• The X-XSS-Protection: 1; mode=block; header, for basic XSS protection in legacy browsers.

If you are using nginx, this would look something like the following:

add_header X-Frame-Options SAMEORIGIN;
add_header X-Content-Type-Options nosniff;
add_header X-XSS-Protection "1; mode=block";
add_header Content-Security-Policy "frame-ancestors 'self'";

For Apache, the configuration looks like:

Header set X-Frame-Options SAMEORIGIN
Header set X-Content-Type-Options nosniff
Header set X-XSS-Protection "1; mode=block"
Header set Content-Security-Policy "frame-ancestors 'self'"

Note: In case you are already setting a Content-Security-Policy header elsewhere, you should modify it to include the frame-ancestors directive instead of adding that last line.

Building From Source

Element is a modular webapp built with modern ES6 and uses a Node.js build system. Ensure you have the latest LTS version of Node.js installed.

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

1. Install or update node.js so that your node is at least the current recommended LTS.
2. Install yarn if not present already.
3. Clone the repo: git clone https://github.com/element-hq/element-web.git.
4. Switch to the element-web directory: cd element-web.
5. Install the prerequisites: yarn install.
   • If you're using the develop branch, then it is recommended to set up a proper development environment (see Setting up a dev environment below). Alternatively, you can use https://develop.element.io - the continuous integration release of the develop branch.
6. Configure the app by copying config.sample.json to config.json and modifying it. See the configuration docs for details.
7. yarn dist to build a tarball to deploy. Untaring this file will give a version-specific directory containing all the files that need to go on your web server.

Note that yarn dist is not supported on Windows, so Windows users can run yarn build, which will build all the necessary files into the webapp directory. The version of Element will not appear in Settings without using the dist script. You can then mount the webapp directory on your web server to actually serve up the app, which is entirely static content.

Running as a Desktop app

Element can also be run as a desktop app, wrapped in Electron. You can download a pre-built version from https://element.io/get-started or, if you prefer, build it yourself.

To build it yourself, follow the instructions at https://github.com/element-hq/element-desktop.

Many thanks to @aviraldg for the initial work on the Electron integration.

The configuration docs show how to override the desktop app's default settings if desired.

config.json

Element supports a variety of settings to configure default servers, behaviour, themes, etc. See the configuration docs for more details.

Labs Features

Some features of Element may be enabled by flags in the Labs section of the settings. Some of these features are described in labs.md.

Caching requirements

Element requires the following URLs not to be cached, when/if you are serving Element from your own webserver:

/config.*.json
/i18n
/home
/sites
/index.html

We also recommend that you force browsers to re-validate any cached copy of Element on page load by configuring your webserver to return Cache-Control: no-cache for /. This ensures the browser will fetch a new version of Element on the next page load after it's been deployed. Note that this is already configured for you in the nginx config of our Dockerfile.

Development

Before attempting to develop on Element you must read the developer guide for matrix-react-sdk, which also defines the design, architecture and style for Element too.

Read the Choosing an issue page for some guidance about where to start. Before starting work on a feature, it's best to ensure your plan aligns well with our vision for Element. Please chat with the team in #element-dev:matrix.org before you start so we can ensure it's something we'd be willing to merge.

You should also familiarise yourself with the "Here be Dragons" guide to the tame & not-so-tame dragons (gotchas) which exist in the codebase.

The idea of Element is to be a relatively lightweight "skin" of customisations on top of the underlying matrix-react-sdk. matrix-react-sdk provides both the higher and lower level React components useful for building Matrix communication apps using React.

Please note that Element is intended to run correctly without access to the public internet. So please don't depend on resources (JS libs, CSS, images, fonts) hosted by external CDNs or servers but instead please package all dependencies into Element itself.

CSS hot-reload is available as an opt-in development feature. You can enable it by defining a CSS_HOT_RELOAD environment variable, in a .env file in the root of the repository. See .env.example for documentation and an example.

Setting up a dev environment

Much of the functionality in Element is actually in the matrix-react-sdk and matrix-js-sdk modules. It is possible to set these up in a way that makes it easy to track the develop branches in git and to make local changes without having to manually rebuild each time.

First clone and build matrix-js-sdk:

git clone https://github.com/matrix-org/matrix-js-sdk.git
pushd matrix-js-sdk
yarn link
yarn install
popd

Then similarly with matrix-react-sdk:

git clone https://github.com/matrix-org/matrix-react-sdk.git
pushd matrix-react-sdk
yarn link
yarn link matrix-js-sdk
yarn install
popd

Clone the repo and switch to the element-web directory:

git clone https://github.com/element-hq/element-web.git
cd element-web

Configure the app by copying config.sample.json to config.json and modifying it. See the configuration docs for details.

Finally, build and start Element itself:

yarn link matrix-js-sdk
yarn link matrix-react-sdk
yarn install
yarn start

Wait a few seconds for the initial build to finish; you should see something like:

[element-js] <s> [webpack.Progress] 100%
[element-js]
[element-js] ℹ ｢wdm｣:    1840 modules
[element-js] ℹ ｢wdm｣: Compiled successfully.

Remember, the command will not terminate since it runs the web server and rebuilds source files when they change. This development server also disables caching, so do NOT use it in production.

Open http://127.0.0.1:8080/ in your browser to see your newly built Element.

Note: The build script uses inotify by default on Linux to monitor directories for changes. If the inotify limits are too low your build will fail silently or with Error: EMFILE: too many open files. To avoid these issues, we recommend a watch limit of at least 128M and instance limit around 512.

You may be interested in issues #15750 and #15774 for further details.

To set a new inotify watch and instance limit, execute:

sudo sysctl fs.inotify.max_user_watches=131072
sudo sysctl fs.inotify.max_user_instances=512
sudo sysctl -p

If you wish, you can make the new limits permanent, by executing:

echo fs.inotify.max_user_watches=131072 | sudo tee -a /etc/sysctl.conf
echo fs.inotify.max_user_instances=512 | sudo tee -a /etc/sysctl.conf
sudo sysctl -p

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When you make changes to matrix-react-sdk or matrix-js-sdk they should be automatically picked up by webpack and built.

If any of these steps error with, file table overflow, you are probably on a mac which has a very low limit on max open files. Run ulimit -Sn 1024 and try again. You'll need to do this in each new terminal you open before building Element.

Running the tests

There are a number of application-level tests in the tests directory; these are designed to run with Jest and JSDOM. To run them

yarn test

End-to-End tests

See matrix-react-sdk for how to run the end-to-end tests.

Translations

To add a new translation, head to the translating doc.

For a developer guide, see the translating dev doc.

Triaging issues

Issues are triaged by community members and the Web App Team, following the triage process.

We use issue labels to sort all incoming issues.