Firefox 93 for developers

Draft: This page is not complete.

This article provides information about the changes in Firefox 93 that will affect developers. Firefox 93 is the current Beta version of Firefox, and will ship on October 5, 2021.

Changes for web developers

Developer Tools

HTML

Removals

CSS

Removals

JavaScript

  • 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 (bug 1670033).

Removals

HTTP

  • 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 (bug 1682995).
  • The default HTTP ACCEPT header for images changed to: image/avif,image/webp,*/* (following addition of support for the AVIF image format). (bug 1682995).

Removals

Security

Removals

APIs

DOM

  • The 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 (bug 1727302).
  • The onslotchange event handler property is now supported on GlobalEventHandlers and ShadowRoot is now supported. This can be used to assign a handler for processing slotchange events, which are fired on <slot> elements when the node(s) contained in the slot change (bug 1501983).
  • Media, WebRTC, and Web Audio

    Events

    • 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 (bug 1717760).

    Removals

    WebAssembly

    Removals

    WebDriver conformance (Marionette)

    Removals

    Changes for add-on developers

    Removals

    Other

    • Support for AVIF images is now enabled by default (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.

    Older versions