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
- User-agent spoofing from the Responsive mode
- Retaining paths panel in memory tool
- Service workers and Push API debugging
- 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).
- Support for the
::backdroppseudo-element has been added (bug 1064843).
- The case-insensitive modifier
[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-sizeare now available (bug 686281).
clip-pathproperty now experimentally supports
circle()on HTML elements (does not support inset() and path()), behind the pref
layout.css.clip-path-shapes.enabledthat defaults to
false(bug 1075457). Interpolation (and therefore animation) of these values is not yet supported.
- Our still experimental grid implementation has been updated:
display-modemedia feature is now supported (bug 1104916).
- The value
text-align-lasthas been renamed to
- The new ES2017 / ES8
Object.entries()methods have been implemented (bug 1232639).
- The deprecated old Proxy API (
Proxy.createFunction) now presents a deprecation warning in the console and will be removed in a future version. Use the standard
Proxyobject instead (bug 892903).
- Support for the deprecated non-standard
replacehas been dropped in non-release builds (bug 1245801).
- As per the new ES2016/ES7 specification, the
Proxyenumerate trap for
for...instatements has been removed (bug 1246318).
Array.prototype.lastIndexOf()methods (and their
TypedArrayequivalents) have been updated to never return
-0as per the ECMAScript specification (bug 1242043).
DOM & HTML DOM
- The property
Document.scrollingElementhas been implemented behind the pref
dom.document.scrollingElement.enabledthat defaults to
Service Worker and related APIs
Request.Request()constructor can now accept a referrer option in its init object (bug 1251448).
Request.referrerPolicyproperty is now supported (bug 1251872).
- Support for the
RTCIceServerdictionary has been updated in keeping with revisions to the WebGL 1.0 specification by adding support for the
credentialTypeproperty. This property is a string which specifies whether the credential is a password or a token. Currently, Firefox only supports
Cache.addAll()now raises a
TypeErrorexception if the response status is not in the
200range (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.enabledpreference, defaulting to false (bug 1268749).
- 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).
- The default value of the
Acceptheader for images is now
- 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
- Firefox 50 for developers
- Firefox 49 for developers
- Firefox 48 for developers
- Firefox 47 for developers
- Firefox 46 for developers
- Firefox 45 for developers
- Firefox 44 for developers
- Firefox 43 for developers
- Firefox 42 for developers
- Firefox 41 for developers
- Firefox 40 for developers
- Firefox 39 for developers
- Firefox 38 for developers
- Firefox 37 for developers
- Firefox 36 for developers
- Firefox 35 for developers
- Firefox 34 for developers
- Firefox 33 for developers
- Firefox 32 for developers
- Firefox 31 for developers
- Firefox 30 for developers
- Firefox 29 for developers
- Firefox 28 for developers
- Firefox 27 for developers
- Firefox 26 for developers
- Firefox 25 for developers
- Firefox 24 for developers
- Firefox 23 for developers
- Firefox 22 for developers
- Firefox 21 for developers
- Firefox 20 for developers