Why develop add-ons for Firefox

Add-ons have been a part of  Firefox since its first version, and they have been integral to its success. The power of the add-on platform and the openness of its ecosystem are key factors that have allowed add-ons to thrive and become one of the most important features in Firefox and other Mozilla applications. Developing add-ons is one of the ways in which you can make a significant and lasting contribution to the Mozilla Mission.

The add-ons platform

The Mozilla add-ons platform is unique in that it is the same platform on top of which front-end application code is written. Firefox code runs alongside add-on code to define how Firefox looks and behaves, and most parts of the Firefox interface can be changed completely with the help of extensions and themes. Innovative add-ons like NoScript and Tree Style Tab would not exist without such an open development platform.

Given the complexity of modern web browsers, add-on developers have a very rich set of APIs to work with. Their breadth can be overwhelming, which is why a simpler set of APIs are provided through the Add-on SDK. The SDK allows you to quickly get started and create good add-ons that cover the most common use cases, while still allowing you to break out of its boundaries and use the low-level APIs available to all extensions.

The Firefox add-on platform extends to Firefox for Android. Depending on the features you want to implement, you can even use the same codebase for your mobile and desktop versions.

Working on add-ons can also serve as a stepping stone to understanding and working on Firefox front-end code. Many add-on developers are regular contributors to Mozilla code, making improvements that help other add-on developers and expanding into areas like security and stability.

The add-ons ecosystem

The main distribution channel for Mozilla add-ons is addons.mozilla.org (AMO). Add-ons listed on AMO are code-reviewed and tested by a team of volunteer add-on developers to ensure they are safe and provide a good user experience. However, Mozilla doesn’t restrict add-on distribution to AMO. Add-on developers are free to distribute their add-ons independently and freely, as long as they follow our Add-on Guidelines.

Add-ons are commonly created with open source principles in mind, so there’s a vast library of current and past add-on work that you can build upon. This also allows developers to continue development of add-ons that can no longer be maintained by their creators or branch existing add-ons in new directions.


There’s a large and active add-on developer community that can help you get started and answer your questions. See the Community and Support section in the sidebar for more information.

Add-on developers are very valuable members of the Mozilla community. The AMO Reviewer Team is composed of experienced add-on developers, and their contributions are rewarded with incentives and invitations to Mozilla events. Many add-on developers have achieved success due to their work or have eventually joined Mozilla as employees.

Creating add-ons helps the Mozilla community grow. It gives our users more tools to customize Firefox and make it their own, continuing its reputation as the most customizable web browser.


Document Tags and Contributors

 Contributors to this page: wbamberg, TWebs, Jorge.villalobos
 Last updated by: wbamberg,