Firefox 52 will be released on March 7th. Here’s the list of changes that went into this version that can affect add-on compatibility. There is more information available in Firefox 52 for Developers, so you should also give it a look.
- Remove support for all NPAPI plugins (except Flash). Read this blog post for more information.
- DnD of multiple shortcuts from desktop only opens one. This enables drag and drop of multiple links to the browser area, which includes some changes like replacing
- The ChromeFilePropertyBag versions of the File constructors are web-observable. This replaces the
Fileconstructors with the static functions
- Drag and Drop:
DataTransfer.typesis wrong type. Instead of
dataTransfer.types.contains, add-ons should use
dataTransfer.types.includes. A shim was added to preserve compatibility, but it’s temporary.
- Crash with Youtube Subtiltle Downloader. This change makes CORS requests from add-ons using an expanded principal not work.
- Deprecate and remove
- Remove web content access to Battery API.
XPCOM and Modules
- Delete toolkit/obsolete. There are some utility objects there used by older add-ons, like
nsUserSettings.jsand the string bundle functions in
nsIEnumeratoras deprecated. These interfaces, particularly
nsISupportsArray, are used in many components add-ons use. They are being replaced with
Let me know in the comments if there’s anything missing or incorrect on these lists. If your add-on breaks on Firefox 52, 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 51.