Firefox 79 for developers

This article provides information about the changes in Firefox 79 that will affect developers. Firefox 79 was released on July 28, 2020.

See also Firefox 79: The safe return of shared memory, new tooling, and platform updates on Mozilla hacks.

Changes for web developers

Developer Tools

Console

Debugger

Other tools

HTML

  • The <iframe> element's sandbox attribute now supports the allow-top-navigation-by-user-activation token (bug 1359867).
  • Setting target="_blank" on <a> and <area> elements implicitly provides the same behavior as also setting rel="noopener" (bug 1522083).

CSS

  • External style sheets are now cached per document group (bug 1599160). Firefox will minimize retrieval and revalidation of cached style sheets when navigating pages on the same origin. A simple reload (for example, F5) will not revalidate the cached CSS files. To load current versions of the style sheets, reload the page bypassing the cache (Cmd/Ctrl + F5).

Removals

JavaScript

HTTP

APIs

DOM

Media, WebRTC, and Web Audio

Removals

  • A number of internal Gecko events — including DOMWindowClose — which were accidentally exposed to the web, are now internal-only as intended (bug 1557407).

WebAssembly

Changes for add-on developers

Older versions