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Maintained by the MDN team at Mozilla.

WebExtensions are a way to write browser extensions: that is, programs installed inside a web browser that modify the behaviour of the browser or of web pages loaded by the browser. They are built on a set of cross-browser APIs, so WebExtensions written for Google Chrome or Opera will in most cases run in Firefox or Edge too.

The "webextensions-examples" repository is a collection of simple but complete and installable WebExtensions. You can use the examples to see how to use the WebExtensions APIs, and as a starting point for your own WebExtensions.

For an index of all the examples, see the "Example extensions" page on MDN.

The examples are made available under the Mozilla Public License 2.0.

How to use "webextensions-examples"

To use the repository, first clone it.

Each example is in its own top-level directory. Install an example in your favourite web browser (installation instructions are below), and see how it works. Each example has its own short README explaining what it does.

To find your way around a WebExtension's internal structure, have a look at the Anatomy of a WebExtension page on MDN.

To use these examples in Firefox, you should use the most recent release of Firefox. Some examples work with earlier releases.

A few examples rely on APIs that are currently only available in pre-release versions of Firefox. Where this is the case, the example should declare the minimum version that it needs in the strict_min_version part of the applications key in its manifest.json file.

Installing an example

There are a couple ways to try out the example extensions in this repository.

  1. Open Firefox and load about:debugging in the URL bar. Click the Load Temporary Add-on button and select the manifest.json file within the directory of an example extension you'd like to install. Here is a video that demonstrates how to do this.
  2. Install the web-ext tool, change into the directory of the example extension you'd like to install, and type web-ext run. This will launch Firefox and install the extension automatically. This tool gives you some additional development features such as automatic reloading.

Learn more

To learn more about developing WebExtensions, see the WebExtensions documentation on MDN for getting started guides, tutorials, and full API reference docs.


If you find a problem, please file a bug.

If you need help, email the dev-addons mailing list or contact the WebExtensions team in the #webextensions IRC channel on


We welcome contributions, whether they are whole new examples, new features, bug fixes, or translations of localizable strings into new languages. Please see the file for more details.