Firefox 83 release notes for developers

This article provides information about the changes in Firefox 83 that will affect developers. Firefox 83 was released on November 17, 2020.

[!NOTE] See also Firefox 83 is upon us on Mozilla hacks

Changes for web developers

Developer Tools

• When using the :screenshot helper command in the Web Console, the --dpr parameter is no longer ignored when taking a fullscreen screenshot using --fullpage (Firefox bug 1645284).
• Developers can use the scroll badge in the Page Inspector to Debug scrollable overflow. Selecting the badge highlights elements that are causing overflow and marks them with the overflow badge (Firefox bug 1669129).

HTML/XML

• The crossorigin attribute is now supported for <link rel=icon> (Firefox bug 1661075).
• The displaystyle attribute is now implemented for all MathML elements (Firefox bug 1666075).

CSS

• The vendor prefixed :-moz-any() is now aliased to the standard {{CSSxRef(":is", ":is()")}} CSS pseudo-class function (Firefox bug 1666086).
• We've added support for CSS Conic Gradients (Firefox bug 1632351) and (Firefox bug 1175958).

JavaScript

• Intl[@@toStringTag] has been added, returning a default value of Intl (recent addition to the ECMA spec). (Firefox bug 1670053)

HTTP

No changes.

APIs

No changes.

WebDriver conformance (Marionette)

• We've removed preliminary support for WebDriver:SwitchToShadowRoot, which hasn't been added to the WebDriver specification yet (Firefox bug 1662468).
• We fixed a bug in WebDriver:Back and WebDriver:Forward that caused Marionette to hang when the navigation was triggered from within an <iframe> that gets removed (Firefox bug 1672758).

Changes for add-on developers

No changes.