Firefox 86 for developers

This article provides information about the changes in Firefox 86 that will affect developers. Firefox 86 is the current Beta version of Firefox, and will ship on February 23, 2021.

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 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. (bug 1551569).
  • The order property was previously incorrectly marked as inactive for grid items. This got fixed in bug 1579017.

HTML

No changes.

SVG

CSS

JavaScript

  • The Intl.DisplayNames built-in object has been enabled by default. This enables the consistent translation of language, region, and script display names:
    // 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 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 bug 1685089.

WebDriver conformance (Marionette)

  • Updated WebDriver:ElementClick to synthesize a mousemove event before the actual click event (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 (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 (bug 1690308).

Removals

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

Changes for add-on developers

Older versions