Firefox 39 for developers

Firefox 39 was released on July 2, 2015. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.

Changes for Web developers

Developer Tools

CSS

HTML

  • A new ARIA role, switch, is now supported (Firefox bug 1136563).
  • Support for <link rel="preconnect"> allowing to anticipate a future connection without revealing any information has been implemented (Firefox bug 1135160).

JavaScript

Interfaces/APIs/DOM

MathML

No change.

SVG

No change.

Audio/Video

No change.

Miscellaneous

Networking

Security

No change.

Changes for add-on and Mozilla developers

No change.

Older versions