Firefox 55 will be released on August 8th. Here’s the list of changes that went into this version that can affect add-on compatibility. There is more information available in Firefox 55 for Developers, so you should also give it a look. Also, if you haven’t yet, please read our roadmap to Firefox 57.
Recently, we turned on a restriction on Nightly that only allows multiprocess add-ons to be enabled. You can use a preference to toggle it. Also, Firefox 55 is the first version to move directly from Nightly to Beta after the removal of the Aurora channel.
- Lazily load built-in SDK modules. The main change of this bug that could affect developers is that Panel views are loaded when the panel is first shown, rather than when it is created.
- Remove Java Addons support from Fennec.
- Replace the
sNextTabParentsetup with something more robust. This mainly affected tab add-ons that use or override
openURIInFrameand related functions.
- Remove the
hiddenwindowspecial case in
CheckLoadURIWithPrincipal. This could affect some add-ons that use the hidden DOM window hack. See comment 11 for details.
- Get rid of
UIEvent.isCharbecause no other browsers support it.
- Disable loading remote jars by default.
- Expose result principal URL (“final channel URL”) on LoadInfo. This can affect add-ons that load custom URLs using special protocols (like about:). As you can see if you follow the link, the bug was reopened. Now the developers are considering alternatives to avoid add-on issues.
XPCOM and Modules
- Move favicons blobs out of
places.sqliteto their own database. This change touches many interfaces, but most adds an optional preferred width argument to some functions (see 1 and 2).
- Compile subscript loader scripts with
loadSubScriptno longer returns a value.
- Avoid using NSS Base64 functions in PSM. This can affect add-ons that use
nsICryptoHMAC. See comment 8 for details.
Let me know in the comments if there’s anything missing or incorrect on these lists. We’d like to know if your add-on breaks on Firefox 55.
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 54.