Getting started with web-ext

Installation

web-ext is a Node-based application. You install it with brew or the NodeJS npm tool.

Install with brew using:

brew install web-ext

Install with npm using:

npm install --global web-ext

web-ext requires the current LTS (long-term support) versions of NodeJS.

To test whether the installation worked, run the following command, which displays the web-ext version number:

web-ext --version

Update

web-ext notifies you when a new version is available. To update, use the same commands as you did to install:

brew install web-ext

or

npm install --global web-ext

Using web-ext

Before you use web-ext, locate an example extension. If you don’t have one, use one from the webextensions-examples repo. If you want to start from scratch, use the community-developed boilerplating tool to start with a fresh extension.

Check your code

Before trying out your extension with the run command or submitting your package to addons.mozilla.org, use the lint command to ensure your manifest and other source files are error-free. If you set strict_min_version in your extension’s manifest file, lint reports on the permissions, manifest keys, and web extension APIs used that are not available in that version.

To check your extension code, cd into your extension’s root directory and enter:

web-ext lint

This uses the addons-linter library to walk through your source code directory and report any errors, such as declaring an unknown permission.

See the lint reference guide to learn more.

Test and debug your extension

In this section, learn how to:

• Test your extension
• Automatically reload your extension
• Test in different versions of Firefox
• Test in Firefox for Android
• Debug in Firefox for Android
• Test unsigned extensions
• Use a custom profile
• Keep profile changes

Test your extension

Test an extension in Firefox by cd'ing into your extension’s root directory and entering:

web-ext run

This starts Firefox and loads the extension temporarily in the browser, just as you can on the about:debugging page. Note that this web-ext method has the same limitations regarding prompts for permissions and restart features as about:debugging.

See the run reference guide to learn more.

Automatically reload your extension

The run command watches your source files and tells Firefox to reload the extension after you edit and save a file. For example, if you change the name property in your manifest.json file, Firefox displays the new name. This makes it easy to try out new features because you can see the effect immediately. The automatic reloading feature is active by default. You use it like this:

web-ext run

You can also press the r key in the web-ext terminal to trigger an extension reload.

If you experience unexpected behavior with the reloading feature, please file a bug. You can also disable reloading like this:

web-ext run --no-reload

Test in different versions of Firefox

To run your extension in a version of Firefox Desktop other than the default, use the --firefox option to specify a full path to the binary file. Here is an example for Mac OS:

web-ext run --firefox=/Applications/FirefoxNightly.app/Contents/MacOS/firefox-bin

On Windows, the path needs to include firefox.exe, for example:

web-ext run --firefox="C:\Program Files\Mozilla Firefox\firefox.exe"

See the run command reference to learn more.

Test in Firefox for Android

To run your extension in Firefox for Android, follow the instructions to set up your computer and device.

With your device connected to your development computer, run:

web-ext run --target=firefox-android

This command displays the device ID for your connected Android device or devices. If you don't see a device ID, check that you set up the device correctly for development.

Now, add the device ID to the command:

web-ext run --target=firefox-android --android-device=<device ID>

If you've installed multiple versions of Firefox on the device, choose one like this:

web-ext run --target=firefox-android ... --firefox-apk=org.mozilla.firefox

The first time you run this command, you may need to grant Android permissions for the APK. This is because the command needs read/write access to the device storage so that Firefox for Android can run on a temporary profile. The web-ext output guides you on how to grant these permissions.

The web-ext command does not alter your Firefox for Android preferences or data. To learn more about how web-ext interacts with your device, run the command with --verbose.

See the run command reference to learn more.

Debug in Firefox for Android

When using web-ext run to test an extension on Firefox for Android, you see a message like this in the console output:

You can connect to this Android device on TCP port 51499

This is a remote debugger port that you can connect to with Firefox's developer tools. In this case, you connect to host localhost on port 51499.

See the Debug your extension guide for more information about debugging an extension on Firefox for Android.

Test unsigned extensions

When you execute web-ext run, the extension is installed and remains installed until you close Firefox. This does not violate any signing restrictions. If instead you create a zip file with web-ext build and try to install it into Firefox, you see an error telling you that the add-on is not signed. To install unsigned extensions, use an unbranded build or development build.

Use a custom profile

By default, the run command creates a temporary Firefox profile. To run your extension with a specific profile use the --firefox-profile option, like this:

web-ext run --firefox-profile=your-custom-profile

This option accepts a string containing the name of your profile or an absolute path to the profile directory. This is helpful if you want to configure settings for the run command.

Keep profile changes

The run command does not save any changes made to the custom profile specified by --firefox-profile. To keep changes, use the --keep-profile-changes option:

web-ext run --keep-profile-changes --firefox-profile=your-custom-profile

This may be helpful if your extension has many different run states.

Package, sign, and publish your extension

In this section learn how to:

• Package your extension
• Sign and submit your extension for publication
• Sign and submit your updated extension for publication
• Sign your extension for self-distribution
• Sign in a restricted environment
• Sign a test version of a listed extension

Package your extension

After testing your extension and verifying that it's working, you can turn it into a package for submitting to addons.mozilla.org using this command:

web-ext build

This outputs a full path to the generated .zip file that can be loaded into a browser.

web-ext build is designed to ignore files that are commonly not wanted in packages, such as .git, node_modules, and other artifacts.

See the build reference guide to learn more.

Sign and submit your extension for publication

When you have confirmed that your extension works as expected, you can publish it on addons.mozilla.org. You can do this using the website or web-ext sign. To use web-ext sign you need to:

• if you're submitting a Manifest V3 extension, ensure that you've set an ID for the extension in its manifest.json file using the key browser_specific_settings.gecko.id.
• create a JSON file containing the metadata needed by addons.mozilla.org to list the extension.
• obtain an API key from addons.mozilla.org.

Create your metadata file

Metadata is required for the first version of an extension listed on AMO. This metadata can include any of the properties of the addons.mozilla.org add-on API Create request JSON object. However, the"categories" and "summary" properties must be provided.

For example:

{
  "version": { "license": "MPL2.0" } },
  "categories": { "firefox": ["shopping", "bookmarks"] },
  "contributions_url": "https://donate.mozilla.org",
  "requires_payment": false,
  "homepage": {
    "en-US": "http://example.org?lang=en-US",
    "fr": "http://example.org?lang=fr"
  },
  "support_email": {
    "en-US": "support@example.org",
    "fr": "support-fr@example.org"
  }
}

Obtain your API key

Visit the addons.mozilla.org credentials page. You must register if you haven't done so before. From this page you obtain:

• The JWT issuer key, a string that looks something like user:12345:67. You supply this to web-ext sign as the API key in --api-key.
• The JWT secret, a string that looks something like 634f34bee43611d2f3c0fd8c06220ac780cff681a578092001183ab62c04e009. You supply this to web-ext sign as the API secret in --api-secret.

Run web-ext sign

You can now run web-ext sign supplying the API key and location of the JSON file containing the metedata.:

web-ext sign --channel=listed --amo-metadata=<path to your metadata JSON file> --api-key=$AMO_JWT_ISSUER --api-secret=$AMO_JWT_SECRET

If you sign a Manifest V2 extension without an explicit ID, addons.mozilla.org generates an ID and web-ext saves it to .web-extension-id in the working directory. Add the ID to the extension's browser_specific_settings.gecko.id key in its manifest.json file. The ID needs to be present to publish updates with web-ext.

See the sign reference guide to learn more.

Sign and submit your updated extension for publication

As you improve and update your extension you want to submit new versions for publication on addons.mozilla.org. You can do this using the website or web-ext sign. To use web-ext sign you need to:

• ensure you've set the extension's ID in the manifest.json key browser_specific_settings.gecko.id.
• create a JSON file containing any updated metadata to be used on addons.mozilla.org.
• obtain an API key from addons.mozilla.org.

Create your metadata file

When publishing an extension update metadata isn't required. However, any of the properties of the addons.mozilla.org add-on API Version Create request JSON object can be provided.

Obtain your API key

Visit the addons.mozilla.org credentials page. You must register if you haven't done so before. From this page you obtain:

• The JWT issuer key, a string that looks something like user:12345:67. You supply this to web-ext sign as the API key in --api-key.
• The JWT secret, a string that looks something like 634f34bee43611d2f3c0fd8c06220ac780cff681a578092001183ab62c04e009. You supply this to web-ext sign as the API secret in --api-secret.

Run web-ext sign

You can now run web-ext sign supplying the API key and location of the JSON file containing the metedata.:

web-ext sign --channel=listed --amo-metadata=<path to your metadata JSON file> --api-key=$AMO_JWT_ISSUER --api-secret=$AMO_JWT_SECRET

See the sign reference guide to learn more.

Sign your extension for self-distribution

As an alternative to publishing your extension on addons.mozilla.org, you can self-host your package file but it needs to be signed by Mozilla first. The following command packages and signs a ZIP file, then returns it as a signed XPI file for distribution:

web-ext sign --channel=unlisted --api-key=$AMO_JWT_ISSUER --api-secret=$AMO_JWT_SECRET

The API options are required to specify your addons.mozilla.org credentials.

• --api-key: the API key (JWT issuer) from addons.mozilla.org needed to sign the extension. This is a string that will look something like user:12345:67.
• --api-secret: the API secret (JWT secret) from addons.mozilla.org needed to sign the extension. This is a string that will look something like 634f34bee43611d2f3c0fd8c06220ac780cff681a578092001183ab62c04e009.

See the sign reference guide to learn more.

Sign in a restricted environment

If you're working in an environment that restricts access to certain domains, you can try using a proxy when signing:

web-ext sign --api-key=... --api-secret=... --api-proxy=https://yourproxy:6000

See the --api-proxy option to learn more.

The following domains are used for signing and downloading files:

• addons.mozilla.org
• addons.cdn.mozilla.net

Sign a test version of a listed extension

If you've listed an extension on addons.mozilla.org, use web-ext to create a signed but unlisted version for testing purposes. For example, you may wish to distribute an alpha or beta version to users for early feedback and testing.

First, change the version number in your manifest.json so that it is different from the latest listed version. Then, create the unlisted version by using the --channel option like this:

web-ext sign --channel=unlisted --api-key=... --api-secret=...

This signs and downloads an XPI file that can be installed into Firefox.

See the sign reference guide to learn more.

Use the configuration file

In this section learn how to:

• Set option defaults in a configuration file
• Automatically discover configuration files

Set option defaults in a configuration file

You can specify --config=my-config.cjs or --config=my-config.mjs to set default values for any option. Here is an example with the build command:

web-ext --config=my-config.mjs build

The file should be a CommonJS module as understood by NodeJS and must export each configuration value. Here is how you would set the default value of --verbose to true:

export default {
  verbose: true,
};

If you want to specify options that only apply to a specific command, you nest the configuration under the command name. Here is an example of adding configuration for --overwrite-dest that only applies to the build command and --firefox that only applies to the run command:

export default {
  // Global options:
  verbose: true,
  // Command options:
  build: {
    overwriteDest: true,
  },
  run: {
    firefox: 'nightly',
  },
};

To create a configuration key for a command line option, you remove the preceding dashes and convert the name to camel case. As you can see from this example, --overwrite-dest was converted to overwriteDest.

If an option can be specified multiple times on the command line then you define it as an array. For example, here is how to specify multiple --ignore-files patterns:

export default {
  ignoreFiles: [
    'package-lock.json',
    'yarn.lock',
  ],
};

web-ext also tries to load its configuration options from a "webExt" property included in the package.json file in the current directory:

{
  "name": "an-extension-src-dir-with-a-package-json",
  "version": "1.0.0",
  ...
  "webExt": {
    "sourceDir": "dist/extension/"
  }
}

Automatically discover configuration files

web-ext loads configuration files in the following order:

• A config file named .web-ext-config.mjs in your home directory, for example:
  • On Windows: C:\Users\<username>\.web-ext-config.mjs
  • On macOS: /Users/<username>/.web-ext-config.mjs
  • On Linux: /home/<username>/.web-ext-config.mjs
• A config property named "webExt" included in a package.json file in the current directory.
• A config file named web-ext-config.mjs in the current directory.

(web-ext also recognizes files named .web-ext-config.cjs as configuration files.)

If a home directory config and a local directory config define the same option, the value from the latter file is used.

For example, creating ~/.web-ext-config.mjs containg:

export default {
  "sign": {
    "apiKey": "<API_KEY>",
    "apiSecret": "<API_SECRET>"
  }
}

Is the equivalent of:

web-ext sign --api-key <API_KEY> --api-secret <API_SECRET>

To disable automatic loading of configuration files, set this option:

web-ext --no-config-discovery run

To diagnose an issue related to config files, re-run your command with --verbose. This tells you which config file affected which option value.

Advanced topics

In this section learn how to:

• Specify different source and destination directories
• Output verbose messages
• View all commands and options
• Detect temporary installation
• Use web-ext from a script

Specify different source and destination directories

The commands use default directories for the extension source and artifact creation (for example, built .zip files). The defaults are:

• Source: The directory you are in.
• Artifacts: A directory called ./web-ext-artifacts, created inside the current directory.

You can specify different source and destination directories using the --source-dir and --artifacts-dir options when running your commands. Their values can be relative or absolute paths, but must always be specified as strings. Here is an example of specifying both options when building an extension:

web-ext build --source-dir=webextension-examples/notify-link-clicks-i18n --artifacts-dir=zips

Output verbose messages

To see in detail what web-ext is doing when you run a command, include the --verbose option. For example:

web-ext build --verbose

View all commands and options

You can list all commands and options like this:

web-ext --help

You can list options for a specific command by adding it as an argument:

web-ext --help run

Detect temporary installation

Your extension can detect whether it was installed using web-ext run, rather than as a built and signed extension downloaded from addons.mozilla.org. Listen for the runtime.onInstalled event and check the value of details.temporary.

Use web-ext from a script

You can use web-ext as a NodeJS module. Here is more information, with example code.

See also

web-ext repo
web-ext command reference