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

  • Firefox now supports remote timestamps on statistics records whose RTCStatsType is remote-outbound-rtp. The RTCRemoteOutboundRtpStreamStats dictionary which is used to provide these statistics now includes the remoteTimestamp property, which states the timestamp on the remote peer at which the statistics were collected or generated (bug 1615191).

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

See also

Older versions