Firefox is Mozilla's popular Web browser, available for multiple platforms including Windows, macOS, and Linux on the desktop and all Android and iOS mobile devices. With broad compatibility, the latest in Web technologies, and powerful development tools, Firefox is a great choice for both Web developers and end users.
Firefox is an open source project; much of the code is contributed by our huge community of volunteers. Here you can learn about how to contribute to the Firefox project and you will also find links to information about the construction of Firefox add-ons, using the developer tools in Firefox, and other topics.
Learn how to create add-ons for Firefox, how to develop and build Firefox itself, and how the internals of Firefox and its subprojects work.
- Developer release notes
Developer-focused release notes; learn what new capabilities for both Web sites and add-ons arrive in each version of Firefox.
- Project documentation
Get detailed information about the internals of Firefox and its build system, so you can find your way around in the code.
- Developer guide
Our developer guide provides details on how to get and compile the Firefox source code, how to find your way around, and how to contribute to the project.
Firefox is available in five channels.
Each night we build Firefox from the latest code in mozilla-central. These builds are for Firefox developers or those who want to try out the very latest cutting edge features while they're still under active development.
Firefox Developer Edition
This is a version of Firefox tailored for developers. Every six weeks, we take the features in Firefox Nightly that are stable enough and create a new version of Firefox Developer Edition. We also add some extra features for developers that are only available in this channel.
After spending six weeks in Firefox Developer Edition, we take the features that are stable enough, and create a new version of Firefox Beta. Firefox Beta builds are for Firefox enthusiasts to test what's destined to become the next released Firefox version.
After stabilizing for another six weeks in Beta, we're ready to ship the new features to hundreds of millions of users in a new release version of Firefox.
Firefox Extended Support Release (ESR)
Firefox ESR is the long-term support edition of Firefox for desktop for use by organizations including schools, universities, businesses and others who need extended support for mass deployments.
- Firefox developer release notes
- This page provides links to the "Firefox X for developers" articles for each Firefox release. These notes let you see what features were added and bugs eliminated in each version of Firefox.
If you find yourself using multiple Firefox channels—or just multiple configurations—on a regular basis, you should read how to use multiple Firefox profiles by turning Firefox's Profile Manager and other profile management tools to your advantage.