Firefox 47 for developers

To test the latest developer features of Firefox,
install Firefox Developer EditionFirefox 47 was released on June 6, 2016. 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

• User-agent spoofing from the Responsive mode
• Retaining paths panel in memory tool
• Service workers and Push API debugging
  • about:debugging dashboard for workers
  • Cached requests are now shown in Network Monitor
  • Support for cache storage in Storage Inspector
• Ability to filter Storage Inspector entries
• Console now detects incomplete input and switches multi-line mode
• Updated breakpoint style in Debugger
• Prevent panels from hiding automatically using the Browser Toolbox, to aid browser and add-on debugging
• Font inspector has been disabled by default
• 3D view has been removed
• Developer tools theme refresh
• Disable the Font Panel (bug 1247723).

HTML

No change.

CSS

• Support for the ::backdrop pseudo-element has been added (bug 1064843).
• The case-insensitive modifier i (like in [foo=bar i]) for attribute selectors has been implemented (bug 888190).
• An experimental implementation of CSS Mask Image properties landed. For the moment, this will only be available on Nightly versions of Firefox.y: shorthand version of mask, as well as mask-repeat, mask-position, mask-size are now available (bug 686281).
• The clip-path property now experimentally supports polygon(), ellipse(), and circle() on HTML elements (does not support inset() and path()), behind the pref layout.css.clip-path-shapes.enabled that defaults to false (bug 1075457). Interpolation (and therefore animation) of these values is not yet supported.
• Our still experimental grid implementation has been updated:
  • align-content: normal behaves now as stretch for grid containers (bug 1237754).
  • The order of column/row values for grid, grid-template, and grid-gap properties has been swapped (bug 1251999).
• The display-mode media feature is now supported (bug 1104916).
• The value true of text-align and text-align-last has been renamed to unsafe (bug 1250342).

JavaScript

• The new ES2017 / ES8 Object.values() and Object.entries() methods have been implemented (bug 1232639).
• The deprecated old Proxy API (Proxy.create and Proxy.createFunction) now presents a deprecation warning in the console and will be removed in a future version. Use the standard Proxy object instead (bug 892903).
• Support for the deprecated non-standard flags argument of String.prototype.match/search/replace has been dropped in non-release builds (bug 1245801).
• As per the new ES2016/ES7 specification, the Proxy enumerate trap for for...in statements has been removed (bug 1246318).
• The Array.prototype.indexOf() and Array.prototype.lastIndexOf() methods (and their TypedArray equivalents) have been updated to never return -0 as per the ECMAScript specification (bug 1242043).

Interfaces/APIs/DOM

DOM & HTML DOM

• The property Document.scrollingElement has been implemented behind the pref dom.document.scrollingElement.enabled that defaults to false (bug 1153322).

WebGL

No change.

IndexedDB

• The IDBKeyRange.includes() method has been implemented (bug 1251498).

Service Worker and related APIs

• The Request.Request() constructor can now accept a referrer option in its init object (bug 1251448).
• The Request.referrerPolicy property is now supported (bug 1251872).

• Service workers and Push have been disabled in the Firefox 45 Extended Support Release (ESR) (bug 1232029).

WebRTC

• Support for the RTCIceServer dictionary has been updated in keeping with revisions to the WebGL 1.0 specification by adding support for the credentialType property. This property is a string which specifies whether the credential is a password or a token. Currently, Firefox only supports "password".

New APIs

No change.

Others

• Cache.add() and Cache.addAll() now raises a TypeError exception if the response status is not in the 200 range (bug 1244764).
• The App installation and management APIs (navigator.mozApps.*) are no longer exposed to non-Firefox OS platforms (bug 1238576).
• Web Crypto API methods can now use the RSA-PSS cryptographic algorithm (bug 1191936).
• The Permissions API has had the Permissions.revoke() method added (bug 1197461).
• The Browser API, which extends the functionality of <iframe>s to allow the creation of frames for displaying web content using HTML — and was previously only available in Firefox OS — is now available to desktop chrome code too (bug 1238160).
• The Notification API's requestPermission() method has been updated from a callback to a promised-based syntax (bug 1241278).
• The Fullscreen API has been updated to the latest spec and unprefixed. Some methods have been renamed or have seen their capitalization changed (bug 743198). Note that this is behind the full-screen-api.unprefix.enabled preference, defaulting to false (bug 1268749).

Audio/Video

• Now WAV file with u-law compression encoding can be played(bug 851530).
• Widevine Content Decryption Module provided by Google Inc. is available via the Encrypted Media Extensions API for use with MP4 (only; see bug 1257716 for EME-with-WebM support) on Windows Vista and later and on Mac OS X enabling migration off Silverlight (bug 1265270).

HTTP

• The default value of the Accept header for images is now */* instead of image/png,image/*;q=0.8,*/*;q=0.5 (bug 1249474).

Networking

No change.

Security

• URL with the view-source: protocol don't open the View Source tool anymore when used from a Web page (bug 1172165).
• The Firefox click-to-activate plugin whitelist has been removed: only Flash doesn't need to be clicked to be activated (bug 1263630).

Changes for add-on and Mozilla developers

Interfaces

• The CSS tokenizer is now available in JavaScript for add-ons (bug 1152033).

FUEL

The FUEL JavaScript library, introduced back in Firefox 3, has been removed. This library was designed to aid in add-on development and with the introduction of the Add-on SDK and, now, by WebExtensions support, is no longer useful. (bug 1090880)

XUL

No change.

JavaScript code modules

No change.

XPCOM

No change.

Other

No change.

See also

• Site Compatibility for Firefox 47

Older versions