Add-on Compatibility for Firefox 51

October 13, 2016

Firefox 51 will be released on January 24th. Note that the scheduled release on December 13th is a point release, not a major release, hence the much longer cycle. Here’s the list of changes that went into this version that can affect add-on compatibility. There is more information available in Firefox 51 for Developers, so you should also give it a look.

General

Let accel-click and middle-click on the new tab button open a new tab next to the current one. This changes the behavior of the new tab button and removes the BrowserOpenNewTabOrWindow function.
Code executed in wrong order with setTimeout after alert. This changes the behavior of the onButtonClick function to make it async.
Drop the prefixed version of visibility API. This removes mozVisibilityState and mozHidden.
Don’t dispatch close event, and remove onclose. This applies to Workers.
Prevent installation of an extension when “*” is used as part of strict_min_version in a WebExtension manifest.json). Minimum versions should always be specific versions, rather than a mask.
Loaded-as-data XML documents should not generate <parsererror>. Some add-ons are relying on this node showing up if an XML document fails to parse.

XPCOM and Modules

Default to the NullPrincipal rather than SystemPrincipal for Favicons. This changes the functions setAndFetchFaviconForPage and replaceFaviconDataFromDataURL. The principal should generally be passed as an argument.
Upload setting wrong Content-Type for files if you downloaded from a server that provided the wrong Content-Type. As explained in comment #36, the way add-ons change the MIME type mappings is now different, via a category rather than directly changing mimeTypes.rdf.
Remove the last references to Actor/FrontClass. While both of these still work for add-ons, they should be considered as deprecated.

New!

Embedded WebExtensions. You can now embed a WebExtension into any restartless add-on, allowing you to gradually migrate your code to the new platform, or transition any data you store to a format that works with WebExtensions.
WebExtension Experiments. This is a mechanism that allows us (and you!) to prototype new WebExtensions APIs.

Let me know in the comments if there’s anything missing or incorrect on these lists. If your add-on breaks on Firefox 51, I’d like to know.

The automatic compatibility validation and upgrade for add-ons on AMO will happen in a few weeks, so keep an eye on your email if you have an add-on listed on our site with its compatibility set to Firefox 50.

Keep up with
all things Firefox.

Your e-mail address

Country

Language

HTML Text

I’m okay with Mozilla handling my info as explained in this Privacy Policy.

We will only send you Mozilla-related information.

Thanks!

If you haven’t previously confirmed a subscription to a Mozilla-related newsletter you may have to do so. Please check your inbox or your spam filter for an e-mail from us.

13 comments on “Add-on Compatibility for Firefox 51”

john wrote on October 13, 2016 at 7:52 pm:

firefox has been saying since 46.0 that web extentions are here bull even a google search has no web extentions firefox also said there would be a seperate web ext section in the addons nothing there either right now there is not one place to download a single web extention whats with that???? i wont comment what i think of firefox right now
1. Will Bamberg wrote on October 14, 2016 at 9:33 am:
  
  > right now there is not one place to download a single web extention whats with that???
  
  You can install WebExtensions from addons.mozilla.org, just like any other kind of add-on. addons.mozilla.org does not tell you whether an add-on is a WebExtension or some other type of add-on, because that’s seen as an internal thing that users don’t need to know about. But this post: https://blog.mozilla.org/addons/2016/08/12/webextensions-taking-root/ said that there were more than 700, and that was a couple of months back.
  
  Scott gave you the same answer, essentially, when you asked this question then: https://blog.mozilla.org/addons/2016/08/12/webextensions-taking-root/#comment-222406
  
  > bull even a google search has no web extentions
  
  I’m not sure what you expect to see in a Google search. Searching for “WebExtensions” gives lots of relevant results, including a repository with some examples to look at. But please note the spelling: “WebExtensions”, not “web extentions”.
  1. john wrote on October 15, 2016 at 11:06 pm:
    
    thank you for replying so fast your right i did ask that question months ago sorry about that i know you guys all work hard but i dont use firefox anymore as most of the addons dont work now. i use are you watching this and 365 sports notifier tab notifier just to name a few no longer work in the latest firefox editions
2. gorhill wrote on October 15, 2016 at 5:22 am:
  
  Here is a good place to find WebExtensions-compatible extensions (search for “webextensions”): http://arewee10syet.com/
  1. gorhill wrote on October 15, 2016 at 5:23 am:
    
    [oops, meant “webextension”, with no “s” at the end]
Kohei Yoshino wrote on October 13, 2016 at 9:59 pm:

Posted the Japanese translation: https://dev.mozilla.jp/2016/10/firefox-51-addon-compatibility/
1. Jorge Villalobos wrote on October 14, 2016 at 2:06 pm:
  
  Thanks!
Luís Miguel (Quicksaver) wrote on October 14, 2016 at 2:09 am:

“Don’t dispatch close event, and remove onclose.” – You might want to specify this is relative to workers, there are other “close” things still around I believe, unless I’m wrong?
1. Jorge Villalobos wrote on October 14, 2016 at 2:07 pm:
  
  Yeah, good point. I’ll fix it.
custom.firefox.lady wrote on October 18, 2016 at 6:43 pm:

Validation links from the “Add-on compatibility with Firefox 50.*” email show warning “Extension is not marked as compatible with Multi Process” even though “Manage My Submissions” at the Developer Hub shows them all as “Multi Process Status: Compatible”. Bug?
1. Jorge Villalobos wrote on October 19, 2016 at 9:19 am:
  
  Can you point me to the add-on? It could be a bug.
  1. custom.firefox.lady wrote on October 19, 2016 at 8:09 pm:
    
    Multiple add-ons; here are the validation links:
    https://addons.mozilla.org/developers/addon/shadglo-library-toolbar/validation-result/561725
    https://addons.mozilla.org/en-US/developers/addon/addons-manager-hilite/validation-result/566186
    https://addons.mozilla.org/en-US/developers/addon/autoclose-sidebar/validation-result/566308
    1. Jorge Villalobos wrote on October 21, 2016 at 1:08 pm:
      
      Thanks, I filed this bug report.

General

XPCOM and Modules

New!

john wrote on October 13, 2016 at 7:52 pm:

Will Bamberg wrote on October 14, 2016 at 9:33 am:

john wrote on October 15, 2016 at 11:06 pm:

gorhill wrote on October 15, 2016 at 5:22 am:

gorhill wrote on October 15, 2016 at 5:23 am:

Kohei Yoshino wrote on October 13, 2016 at 9:59 pm:

Jorge Villalobos wrote on October 14, 2016 at 2:06 pm:

Luís Miguel (Quicksaver) wrote on October 14, 2016 at 2:09 am:

Jorge Villalobos wrote on October 14, 2016 at 2:07 pm:

custom.firefox.lady wrote on October 18, 2016 at 6:43 pm:

Jorge Villalobos wrote on October 19, 2016 at 9:19 am:

custom.firefox.lady wrote on October 19, 2016 at 8:09 pm:

Jorge Villalobos wrote on October 21, 2016 at 1:08 pm: