Firefox 90 for developers

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This article provides information about the changes in Firefox 90 that will affect developers. Firefox 90 is the current Beta version of Firefox, and will ship on July 13, 2021.

Changes for web developers

Developer Tools

HTML

Removals

CSS

Removals

JavaScript

Removals

HTTP

  • The HTTP fetch metadata request headers (Sec-Fetch-*) are now supported. These headers provide servers with additional context about requests, including whether they are same-origin, cross-origin, same-site, or user-intiated, and where/how the requested data is to be used. This allows servers to mitigate against several types of cross-origin attacks (bug 1695911).

Removals

Security

Removals

APIs

DOM

  • Support was added for the deprecated WheelEvent properties: WheelEvent.wheelDelta, WheelEvent.wheelDeltaX, and WheelEvent.wheelDeltaY. This allows Firefox to work with a small subset of pages that were broken by recent compatibility improvements to WheelEvent (bug 1708829).

Media, WebRTC, and Web Audio

Removals

WebAssembly

Removals

WebDriver conformance (Marionette)

Removals

Changes for add-on developers

Removals

Older versions