Cross-browser extensions, available now in Firefox

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?

Build WebExtensions

Port an existing Chrome extension

About Potch

Potch is a Web Platform Advocate at Mozilla.

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  1. aney1

    I have written a script that is collecting the number of addons by type on AMO. The data can be viewed on a Google Sheet with charts here:

    June 8th, 2017 at 11:39

  2. Michael M.

    I’m slightly confused about which name means what. There is the term “WebExtension”. According to it refers to those cross-browser extensions, but as far as I have heard it being used, it is usually just used for the Firefox implementation. I.e. “I’m writing a WebExtension.” means “This works in Firefox. It might work in other browsers, too, but I didn’t test it, and I don’t really care for it.” And actually, even uses “WebExtensions” in that sense to differentiate it from Chrome/Opera browser extensions., on the other hand seems to call those browser extensions just “Browser Extensions”. This is a rather generic term, and nobody would ever say “I’m writing a Browser Extension browser extension.”

    So what is the best term to use instead of the lengthy “I’m writing a browser extension using that cool new standard, and it actually works both in Firefox and in Chrome!”?

    June 10th, 2017 at 00:24

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