Firefox 88 for developers

This article provides information about the changes in Firefox 88 that will affect developers. Firefox 88 was released on April 19, 2021.

• The toggle button for switching between raw and formatted response views has been implemented (bug 1693147). For examples, see Network request details > Response tab.

No changes.

• The :user-valid and :user-invalid pseudo-classes have been implemented (bug 1694141).
• The image-set() functional notation is now enabled (bug 1698133), and was made available for content and cursor in bug 1695402 and bug 1695403.
• 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 has been implemented, and is the new initial value for the property (bug 1694748).
• The outline CSS property has been updated to follow the outline created by border-radius. As part of this work the non-standard -moz-outline-radius property has been removed. (bug 315209 and bug 1694146.)

Removals

• The :-moz-submit-invalid pseudo-class has been hidden behind a preference, thereby 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).

• 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).

No changes.

DOM

• Code can now use the new static method AbortSignal.abort() to return an AbortSignal that is already set as aborted (bug 1698468).

• Marionette will no longer be enabled unless the --marionette command line argument or the MOZ_MARIONETTE environment variable is specified. As such the marionette.enabled preference is no longer used. With this change the state of navigator.webdriver now correctly reflects the enabled state of Marionette (bug 1593343).
• Fixed a bug where pointer actions other than down and up inappropriately led to buttons being pressed (bug 1686361).
• Fixed a race condition in WebDriver:GetCurrentURL that could have led the command to return the URL of the previously opened page, or even a hang in Marionette (bug 1664881).

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