Firefox 99 for developers

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This article provides information about the changes in Firefox 99 that will affect developers. Firefox 99 is the current Beta version of Firefox and will ship on April 5, 2022.

Changes for web developers

Developer Tools

HTML

Removals

CSS

Removals

JavaScript

Removals

HTTP

Removals

Security

Removals

APIs

  • navigator.pdfViewerEnabled is now enabled, and is the recommend way to determine whether a browser supports inline display of PDF files when navigating to them. Sites that use the deprecated properties navigator.plugins and navigator.mimeTypes to infer PDF viewer support should now use the new property, even though these now return hard-coded mock values that match the signal provided by pdfViewerEnabled (bug 1720353).
  • The Network Information API was previously enabled on Android (only), but is now disabled by default on all platforms. The API is on the path for removal because it exposes a significant amount of user information that might be used for fingerprinting. (bug 1720353).

DOM

Media, WebRTC, and Web Audio

Removals

WebAssembly

Removals

WebDriver conformance (Marionette)

Removals

Changes for add-on developers

Removals

Other

Older versions