Extend the Web

Get help creating and publishing Firefox add-ons that make browsing smarter, safer, and faster.

You’ll find the resources you need, whether you’re getting started with extension development, preparing to launch your innovation, or developing a custom enterprise solution.

Why Create Extensions on Firefox?

Get your great idea into the hands of millions of Firefox users. Join an international community of developers. Be supported every step of the way. And, when you build for Firefox first, it’s easy to port your extension to other browsers, saving you valuable development time.

Learn more about extensions

Cool Things Add-ons Can Do

Tinker with Tabs

Your extension can control browser tabs. Use the API to open, close, move, hide, and perform other tab management actions.

Learn more about tabs

Integrate Web Search

Use Firefox's powerful built-in search capabilities to open up the web for users from within your own extension.

Learn about enhancing content

Add Innovative Features

Think the browser is missing a feature, such as a built-in calculator, music streaming, or language translation? Add a toolbar button to expose your extension's new capabilities.

Visit example

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

Build extensions

It's easy to create your cross-browser extension for Firefox. Where your development journey begins depends on your skill and experience.

Brand new to extensions development?

MDN web docs will onboard you to the basics. With tutorials from simple user interface changes to complex event handling, MDN covers the structure and API behind extensions. Once you know the fundamentals, come back here to learn how Firefox takes extension development to the next level.

Learn the fundamentals on MDN

Ready to build an extension for Firefox?

If you know the basics of extension development, you’re ready to create an extension for Firefox. We’ve got all the resources you need right here. Learn about cross-browser development. Get tips on testing. Make user updates smooth and painless.

Learn

Develop

Test & Debug

Publish

Manage

Build secure extensions

Mozilla takes the safety and privacy of its users very seriously. Be sure to review and follow these practices and policies so you can make your great idea a reality.

Learn about security best practices

Learn about our policies

Build across browsers

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

Learn about browser differences

Port a Google Chrome Extension

Your extension might already be compatible!

See if your extension works in Firefox. Simply upload your .crx file to the Developer Hub.

Need some extra help along the way?

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

Extension Workshop