Firefox 93 release notes for developers - Content

This article provides information about the changes in Firefox 93 that will affect developers. Firefox 93 was released on October 5, 2021.

[!NOTE] See also Lots to see in Firefox 93 on Mozilla Hacks.

Changes for web developers

The ARIA meter role has been implemented (Firefox bug 1727616).
The UI for <input type="datetime-local"> has been implemented. (Firefox bug 1283388).

The small-caps keyword is now supported for the {{cssxref("font-synthesis")}} property (Firefox bug 1706080).

Class static initialization blocks are now supported, allowing more flexible initialization of {{jsxref("Classes/static", "static")}} properties (Firefox bug 1725689).
The properties imageOrientation and premultiplyAlpha can be passed to the method {{domxref("Window.createImageBitmap()")}} and {{domxref("WorkerGlobalScope.createImageBitmap()")}} using the options object (Firefox bug 1367251).
{{jsxref("Intl.supportedValuesOf()")}} is now supported, allowing code to enumerate values supported by an implementation, This might be used, for example, to download a polyfill for just the missing category of values (Firefox bug 1670033).

The SHA-256 algorithm is now supported for HTTP Authentication using digests. This allows much more secure authentication than previously available using the MD5 algorithm (Firefox bug 472823).
The default HTTP {{HTTPHeader("ACCEPT")}} header for images changed to: image/avif,image/webp,*/* (following addition of support for the AVIF image format). (Firefox bug 1682995).

{{domxref("ElementInternals.shadowRoot")}} and {{domxref("HTMLElement.attachInternals")}} are now supported (Firefox bug 1723521).
The value device-pixel-content-box is now supported for {{domxref("ResizeObserver.Observe()")}} (Firefox bug 1587973).
The {{domxref("Window.reportError()")}} and {{domxref("WorkerGlobalScope.reportError()")}} is now supported, allowing scripts to report errors to the console or global event handlers, emulating an uncaught JavaScript exception (Firefox bug 1722448).

The {{domxref("Element.securitypolicyviolation_event","onsecuritypolicyviolation")}} global event handler property is now supported. This can be used to assign a handler for processing securitypolicyviolation events fired when there is a Content Security Policy violation (Firefox bug 1727302).
The onslotchange event handler property is now supported on {{domxref("HTMLSlotElement")}} and {{domxref("ShadowRoot")}}. This can be used to assign a handler for processing slotchange events, which are fired on {{HTMLElement("slot")}} elements when the node(s) contained in the slot change (Firefox bug 1501983).

KeyboardEvent.initKeyEvent() has been moved behind the preference dom.keyboardevent.init_key_event.enabled and is disabled by default. The method is not present in any current specification or supported in other current browsers (Firefox bug 1717760).

Fixed a bug which caused WebDriver:Print to fail for large documents (Firefox bug 1721982).

Sidebars are now included in {{WebExtAPIRef("extension.getViews")}} when windowId is specified (Firefox bug 1612390).

Support for AVIF images is now enabled by default (Firefox bug 1682995). This format has excellent compression and no patent restrictions (it was developed by the Alliance for Open Media). Firefox can display still images, with colorspace support for both full and limited range colors, and image transforms for mirroring and rotation. The preference image.avif.compliance_strictness can be used to adjust the compliance strictness with the specification. Animated images are not supported.