Firefox 52 for developers

Firefox 52, based on Gecko 52, will ship in March 2017. This article provides information about the changes in this release that will affect developers. Nightly builds of what will become Firefox 52 are currently available on the Nightly channel. Some experimental features whose release dates are uncertain or undecided are discussed on the page Experimental features in Firefox. Some features described there may be available in Firefox 52.

Changes for Web developers

Developer Tools

• console.groupCollapsed() now collapses the logged group as expected (bug 1088360).

HTML

No change.

CSS

• Added :focus-within pseudo-class (bug 1176997).
• clip-path shapes don't transition between percent and pixel coordinates (bug 1266570).
• Add support for display:flex/grid and columnset layout inside <button> elements(we are the only modern web rendering engine to not have this particular behavior on <button style="display:flex">. So from a web compatibility perspective, we should probably align with the other engines on this.) (bug 984869).
• [css-grid] Implement Grid container Baselines (bug 1151204).
• Implement interpolation between numeric color and currentcolor (bug 1299741).
• Remove -moz-use-text-color from color properties (bug 1306214).
• Unprefix css3 multi-column properties (and add back -moz prefixed versions as aliases, for now) (bug 1300895).
• [css-flexbox] Implement flexbox layout for "justify-content: space-evenly" & "align-content: space-evenly" (bug 1235922).
• Support subpixel AA in CSS mask / clip-path (bug 1305259).
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JavaScript

• Added rest parameter destructuring (bug 1243717).
• Shipped exponentiation operator (**) (bug 1291212).

Interfaces/APIs/DOM

DOM & HTML DOM

• Ship the selection events API (bug 1309612).
• Support Event.composed (bug 1292063).
• Fullscreen request should only be allowed for HTML element, <svg>, and <math> (bug 1305928).

Canvas

No change.

WebGL

No change.

IndexedDB

No change.

Service Workers

No change.

WebRTC

• The MediaDevices.ondevicechange event handler and corresponding devicechange event, which were implemented but disabled by default on Mac only in Firefox 51, have been implemented on Windows and Linux and are now enabled by default.

New APIs

No change.

Others

No change.

MathML

No change.

SVG

No change.

Audio/Video

No change.

HTTP

No change.

Networking

No change.

Security

No change.

Changes for add-on and Mozilla developers

Interfaces

• nsIDroppedLinkHandler.dropLinks method and nsIDroppedLinkItem interface have been added to handle dropping multiple items (bug 92737).

XUL

• tabbrowser.loadTabs(uris, params) method overload has been added (bug 92737).
• browser.droppedLinkHandler function signature has been changed (bug 92737).

No change.

JavaScript code modules

No change.

XPCOM

No change.

Other

No change.

See also

• Site Compatibility for Firefox 52

Older versions