Firefox 91 for developers

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This article provides information about the changes in Firefox 91 that will affect developers. Firefox 91 is the current Beta version of Firefox, and will ship on August 8, 2021.

Changes for web developers

Developer Tools

HTML

Removals

CSS

Removals

  • The non-standard -moz-outline-radius property has been removed (bug 1715984). The property has not been usable by web developers since Firefox 88, this completes the removal.

JavaScript

Removals

HTTP

Removals

Security

Removals

APIs

DOM

Media, WebRTC, and Web Audio

Removals

WebAssembly

Removals

WebDriver conformance (Marionette)

Removals

Changes for add-on developers

Removals

Older versions