Firefox 86 release notes for developers

Changes for web developers

Developer Tools

• The cd() web console helper function, which was deprecated in Firefox 74, has now been removed. The <iframe> context picker tool described in Working with iframes serves the same purpose, but is much better! For more information see Firefox bug 1607741.
• The different margin and padding shorthand and longhand properties are now marked as inactive on internal table elements because they have no effect on them. (Firefox bug 1551569).
• The order property was previously incorrectly marked as inactive for grid items. This got fixed in Firefox bug 1579017.

HTML

No changes.

SVG

• SVG filters can now use the <feComposite> element with the lighter operator (Firefox bug 1518099). This operator sums the pixels of two source graphics.

CSS

• The :autofill pseudo-class is now enabled, with -webkit-autofill as an alias (Firefox bug 1685675) and (Firefox bug 1475316).
• The list-style-image property now accepts any valid <image> (Firefox bug 1685078).

JavaScript

• The Intl.DisplayNames built-in object has been enabled by default. This enables the consistent translation of language, region, and script display names:

  js

  // Get English currency code display names
  let currencyNames = new Intl.DisplayNames(["en"], { type: "currency" });
  // Get currency names
  currencyNames.of("USD"); // "US Dollar"
  currencyNames.of("EUR"); // "Euro"
  

  For more information see Firefox bug 1654116.

APIs

DOM

• Window.name is now reset to an empty string if a tab loads a page from a different domain, and restored if the original page is reloaded (e.g., by selecting the "back" button). This prevents an untrusted page from accessing any information that the previous page might have stored in the property (potentially the new page might also modify such data, which might then be read by the original page if it was reloaded). For more information see Firefox bug 1685089.
• EventTarget.addEventListener() now supports the signal option. This option allows an AbortSignal to be passed to the method. The AbortSignal can later be used to remove the listener by calling abort(). For more information see Firefox bug 1679204.

WebDriver conformance (Marionette)

• Updated WebDriver:ElementClick to synthesize a mousemove event before the actual click event (Firefox bug 1684002).

Known bugs

• WebDriver commands following a call to WebDriver:SwitchToFrame can fail with a "no such window" error if the frame's content hasn't yet finished loading (Firefox bug 1691348).
• After a cross-group page navigation, accessing a previously-retrieved element might not always raise a "stale element" error, and can also lead to a "no such element" error. To prevent this, set the marionette.actors.enabled preference to false (Firefox bug 1690308).

Removals

• Removed support for the deprecated Marionette:ActionChain and Marionette:MultiAction commands (Firefox bug 1683755).

Changes for add-on developers

• Host permissions now grant access to privileged parts of the tabs API (Firefox bug 1679688).
• focused: false is now ignored when set as an option in a windows.create() call (Firefox bug 1253129).
• identity.getRedirectURL now supports a loopback address, see Getting the redirect URL for details (Firefox bug 1614919).
• The page ID is now returned as part of history.onTitleChanged (Firefox bug 1678611).