We’re modernizing the way developers build extensions for Firefox! We call the new APIs WebExtensions , because they’re written using the technologies of the Web: HTML, CSS, and JavaScript. And just like the technologies of the Web, you can write one codebase that works in multiple places.

WebExtensions APIs are inspired by the existing Google Chrome extension APIs, and are supported by Opera, Firefox, and Microsoft Edge. We’re working to standardize these existing APIs as well as proposing new ones! Our goal is to make extensions as easy to share between browsers as the pages they browse, and powerful enough to let people customize their browsers to match their needs.

Want to know more?

Check out WebExtensions documentation on MDN.

Read more about the advantages of WebExtensions for developers on the Add-ons Blog.

Build WebExtensions

Build your first WebExtension by following this tutorial on MDN.

Use the command line? The web-ext CLI tool makes your development workflow a pleasure.

Port an existing Chrome extension