Why Create Extensions on Firefox?

Build on the web’s most customizable browser. Get your great idea into the hands of millions of users. Join an international community of developers in the movement to put people in control of their online lives. (P.S. There’s no cost to participate!)

Learn more about extensions

Anatomy of an Extension

An extension is a simple collection of files that modify the browser’s appearance and behavior. It can add user interface elements, alter content, or perform background tasks that enhance browsing.

Learn more about extension anatomy

Manifest.json

Manifest.json

How to Build An Extension

Firefox extensions are made with the same technologies used to build the web. They employ a modern promise-based API to communicate with and customize the browser.

Build an Extension in Less Than 5 Minutes

Build Across Browsers

Firefox is at the forefront of cross-browser compatibility. Firefox extensions are built using the WebExtensions API, so your creation will be accessible to users no matter what browser they use.

Learn about browser differences

Bring Your Extension to Firefox

Bring Your Extension to Firefox

Already have an extension that works in Chrome? Bring your app to Firefox in a few easy steps.

Get Started

Create a New Extension

Create a New Extension

Starting from scratch? It’s easy and fast to create your cross-browser extension in Firefox.

Get Started

Your extension might already be compatible!

See if your extension works in Firefox. Simply upload your .crx file.

Test your extension

Attract Users with Content and Design

You’ll want users! The shortest route to getting, and keeping them, is creating a great experience and compelling product page.

What’s Great Content and Design?

What’s Great Content and Design?

Featuring Madhava Enros, Senior Director of Firefox User Experience, and Dietrich Ayala, extension developer.

Watch the video

Optimize Your Product Page

Optimize Your Product Page

People spend just seconds on your product page. Make those seconds count with stellar content and visuals.

Find out how

Focus on Usability

Focus on Usability

Build in UX best practices and 
the positive reviews and ratings 
will follow.

Learn more about usability

Connect with the Community

When you build on Firefox, you build with a community of extension developers. And they’re eager to share their expertise and answer your questions.

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