Firefox 88 for developers

This article provides information about the changes in Firefox 88 that will affect developers. Firefox 88 is the current Beta version of Firefox, and will ship on April 20, 2021.

Removals

Removals

• The :user-valid and :user-invalid pseudo-classes have been implemented (bug 1694141).
• The image-set() functional notation is now implemented for content and cursor (bug 1695402), and (bug 1695403).
• The image-set() functional notation is now enabled (bug 1698133).
• The default monospace font for MacOS has been changed to Menlo (bug 1342741).
• The collapse value of visibility is now implemented for ruby annotations (bug 1697529).
• The alternate value for ruby-position is now implemented, and is the new initial value for the property (bug 1694748).

Removals

• The :-moz-submit-invalid pseudo-class has been hidden behind a preference, therefore removing it from web content (bug 1694129).
• Default styling for the non-standard :-moz-ui-invalid and :-moz-ui-valid has been removed (bug 1693969).

• Added support for RegExp match indices (bug 1519483).
• Intl.DisplayNames() and Intl.ListFormat() now have stricter checking that options passed to the constructor are objects, and will throw an exception if a string or other primitive is used instead (bug 1696881).

Removals

• FTP has been disabled on all releases (preference network.ftp.enabled now defaults to false), with the intent of removing it altogether in Firefox 90 (bug 1691890). Complementing this change, the extension setting browserSettings.ftpProtocolEnabled has been made read-only, and web extensions can now register themselves as protocol handlers for FTP (bug 1626365).

Removals

Removals

DOM

• Code can now use the new static method AbortSignal.abort() to return an AbortSignal that is already set as aborted. This is useful when the signal is requested/created after the associated operation has already been aborted. For more information see bug 1698468.

Media, WebRTC, and Web Audio

Removals

• The Presentation API is no longer supported. For more information see bug 1697680.

Removals

Removals

• url can now be used to limit the properties for which the tabs.onUpdated event is triggered (bug 1680279).

Removals