If you are looking for documentation on how to develop an extension with WebExtensions APIs with Firefox, please check out MDN.
This page is an introduction to Mozilla's implementation of WebExtensions, a new browser extension API; a cross-browser system for developing extensions. The goals of this API are:
- Porting add-ons to and from other browsers should be easier.
- Reviewing add-ons for addons.mozilla.org (AMO) should be easier.
- Compatibility with multiprocess Firefox (Electrolysis).
- Changes to Firefox's internal code should be less likely to break add-ons.
- WebExtensions APIs should be easier to use than the existing Firefox XPCOM/XUL APIs.
- WebExtensions APIs should maintain acceptable security and privacy standards.
Please note: the API is called "WebExtensions" because it can be found in search engines; "Web Extensions" (with a space) does not yield relevant results. Information on terminology usage is available here.
- Bugs are filed in Bugzilla under Toolkit > WebExtensions, find or create a bug
- Need documentation
- Untriaged (note: this is different from the untriaged component)
- Design Decision Needed
- Advisory Group
- All bugs
- Closed in past 17 days
To keep track of priorities for Firefox 57, we are using the webextensions tracking flag. You can nominate a bug by using the flag with a ?. Bugs that are not on the tracking flag may still be worked but, but will not be a priority. All bugs must have a priority and preferably an assignee. All P1 bugs must have an assignee.
Communication and meetings
- There is a list of prioritized WebExtension APIs publicly available as part of ongoing Add-ons work.
- There are developer resources to help you through the migration.
- Currently every week there is a public triage meeting of the bugs we hope to complete.
- Every week there is a triage of WebExtensions APIs.
- Join the mailing list at email@example.com.
- Join us on IRC at #webextensions or #addons
Testing WebExtensions APIs
See Your first extension on MDN.
At this time, all APIs are accessible through the chrome.* and browser.* namespace. When we begin to add our own APIs, we expect to add them to the browser.* namespace.
Extensions developed with WebExtensions APIs are compatible with Electrolysis. They run in the main Firefox process (except for content scripts, which run in the same process as web content). We are considering a plan to run extensions in a separate process (or possibly the content process) eventually, see 1190679 for more details.
Technical details about the implementation are published at WebExtensions/Implementing_APIs_out-of-process.
Testing details are published at WebExtensions/Testing-out-of-process.
Extensions are packaged as standard Zip files, but with
.xpi extensions. In the future, we're planning to move towards what the W3C WG recommends.
See https://developer.chrome.com/extensions/manifest for a complete list of manifest directives.
API support status
The list of APIs and their status is now maintained on MDN. We intend to fix any of the exceptions listed there.
- If you're experienced with Mozilla infrastructure and would like to develop WebExtensions APIs directly for Firefox, here is a list of approved APIs that you can start contributing to.
- If you'd like to become familiar with Mozilla infrastructure so you can develop WebExtensions APIs directly for Firefox, follow these steps:
- If you just want to tinker with WebExtensions APIs without having to build Firefox, WebExtensions Experiments is for you!
- If you simply want to request a WebExtensions API, please read this information before filing a bug.
Please see the hacking guide for information about contributing code to the WebExtensions project.
Please see https://webextensions-experiments.readthedocs.io/en/latest/ for some information on Experiments which might be useful for contributing.
Here is a list of all add-on contribution opportunities.