New WebExtensions Guides and How-tos on MDN

The official launch of WebExtensions is happening in Firefox 48, but much of what you need is already supported in Firefox and AMO ( The best place to get started with WebExtensions is MDN, where you can find a trove of helpful information. I’d like to highlight a couple of recent additions that you might find useful:

Thank you to Will Bamberg for doing the bulk of this work. Remember that MDN is a community wiki, so anyone can help!

12 responses

  1. Joe Ertaba wrote on :

    Is it yet possible to use WebExtensions in SDK based or XUL based add-ons?

    1. Jorge Villalobos wrote on :

      You want to follow this bug. In short, not yet.

      1. Caspy7 wrote on :

        I kind of wonder if he might have actually meant a way to embed webextension APIs into SDK or XUL addons. Either way, I’m curious to that question.

        I have a vague recollection of a blog post saying this was possible (and how) but cannot find it now.

  2. Bruce wrote on :

    I’m looking at nativeMessaging in 49. I ported an NPAPI plugin to Chrome a while back. In Firefox I use js-ctypes but would like to drop in the Chrome extension. This extension is whitelisted to a couple of sites using the “externally_connectable” manifest described at This means I don’t need a content script as I can connect directly from the web page using chrome.runtime.connect. As far as I can tell externally_connectable is not supported. Are there plans to?

  3. ismnoiet wrote on :

    Great, keep the good work.

  4. franz wrote on :

    When an extension gets updated on a user’s PC from being a legacy addon to being a WebExtension, is there a way to access the settings and toolbar button position from the the legacy addon?

    1. Jorge Villalobos wrote on :

      I’m not sure what you mean. When the add-on is updated, the legacy code is deactivated and then the WebExtension is installed, so there’s nothing that can be done from the legacy add-on. Are you saying there’s a problem with the button position after an upgrade?

      1. franz wrote on :

        Not aware of any problem with the button position.

        Regarding user settings, I just found that there’s something underway that would allow handing over those to a Webextension:

  5. (y) wrote on :


  6. bruce wrote on :

    Are there any plans to support the “externally_connectable” manifest entry described at (been looking at 49).

    1. Jorge Villalobos wrote on :

      runtime.connect is being implemented, and I think that manifest flag is part of it. The only mention of the flag I see is on this bug.

  7. Thanhkhiet wrote on :

    Great, thanks. Keep up the good work