To test the latest developer features of Firefox,
install Firefox Developer Edition Firefox 45 was released on March 8, 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
- Full-text search in the Page Inspector
- Heap snapshot diffing in the Memory tool
- DomContentLoaded and load events shown in the Network Monitor
- Animation inspector improvements
- Content Security Policy can now be set directly on the
<meta>element (bug 663570).
- The attribute
referrerhas been renamed
- Changes in the viewport, or a resize, now trigger the reselection of responsive images for
<img srcset>(bug 1166138).
word-spacingnow allows percentage values (bug 1038663).
- Our implementation of CSS Grids has been improved and is no more considered experimental; it is now activated by default in nightly and developer edition, but not for beta and release (bug 1000592):
- Gutters, that is the
grid-gapproperties are now supported (bug 1176792).
- The implied minimum size of grid Items, that is the special
autobehavior has been implemented (bug 1176775).
justify-selfare now supported on grid layouts (bug 1151213).
justify-contentare now supported on grid layouts (bug 1151214).
- Resolved value of grid-template-columns,grid-template-rows in px units (bug 978212).
- The related feature
display: contents has been supported since Firefox 37
- Gutters, that is the
- Implement full support for CSS Box Alignment for CSS Grid, support the missing values:
right,last-baseline,space-evenly(bug 1176782). CSS Box Alignment currently applies only to CSS Flexbox and CSS Grid.
- [css-grid][css-flexbox] Implement grid/flex layout for <fieldset> (bug 1230207).
inline-endvalues have been added to
clear(bug 1122918). They are enabled by default on Nightly and Aurora (Dev edition), as well as on Firefox OS; to activate it on a release or beta version, you need to flip the
text-emphasis-positionhave been implemented; they are disabled by default (set
layout.css.text-emphasis.enabledto true to activate them (bug 1040668).
-webkitprefixed properties and values have been added for web compatibility, behind the preference
layout.css.prefixes.webkit, defaulting to
- ES2015 (ES6) Classes are now enabled by default (bug 1197932).
- Expression closures are deprecated and will now present a warning in the console (bug 995610).
String.prototype.replacedoes not restore RegExp static properties after executing function parameter anymore (bug 1226936).
Math.random()has been updated to the better XorShift128+ algorithm (bug 322529).
DOM & HTML DOM
- For compatibility, the non-standard property
Node.innerTexthas been implemented (bug 264412).
HTMLImageElement.srcsetattribute now reacts to resize/viewport changes (bug 1166138).
Our implementation of WebGL 2 has been extended:
- Support of programs and shaders has been added (bug 1048743).
- Support for uniforms and attributes has been added (bug 1048745).
- Framebuffer objects have been implemented (bug 1048732).
- Renderbuffer objects have been implemented (bug 1048733).
FetchEvent.clientIdhave been implemented (bug 1222464.)
Clients.openWindow()has been implemented (bug 1172870.)
- The options object that can be passed as a parameter when invoking
Clients.matchAll()can now include an
includeUncontrolledproperty. This is a
Boolean— if set to
true, the matching operation will return all service worker clients who share the same origin as the current service worker. Otherwise, it returns only the service worker clients controlled by the current service worker. The default is
- Web Speech Synthesis API has been implemented on Firefox Desktop (bug 1003439).
Window.onstorageevent handler property has been added.
- The interface
ComputedTiminghave been added to our experimental implementation of Web Animations API (bug 1108055).
Document.onselectionchangeevent handler property has been added (bug 1231193).
- After removing a video track from a media stream by calling
MediaStream.removeTrack()you can nowadd another video track later using
MediaStream.addTrack()and have it played (bug 1223696).
- SVG stroke hit-testing is buggy when cairo is the Moz2D backend (bug 676001).
- Unable to interact with elements who have large transform / translate values (bug 1217012).
- Fixed: Regression (since Firefox 41) whereby audio playback was stuttering due to duration time rounding errors (bug 1222866.)
jar:protocol has been disabled by default when accessed from Web content; you may enable this if necessary by setting the
Content-Security-Policycan now be specified using a
<meta>element (bug 663570).
- Support of the
child-srcCSP policy directive has been implemented (bug 1045891).
- EV certificates with a validity greater than 27 months are now considered and handled as DV certificates (bug 1222903).
Changes for add-on and Mozilla developers
- Tab Groups have been removed.
Starting in Firefox 45, search plugins located in the user's profile's
searchplugins directory are no longer automatically loaded on startup. Instead, a list of user-installed plugins is maintained and only those plugins are loaded. In effect, this means that the only ways to install new search plugins are for the user to do so in the Firefox UX (via OpenSearch discovery, for instance) or for an add-on to install it. Also, when a new search plugin is installed, more information is recorded about where it came from, for future use by profile debugging and cleaning tools.
- WebIDL constructors could be called without the
newoperator in chrome context. Now such code will raise a
TypeErroras in Web content since Firefox 30. For example,
var req = XMLHttpRequest();needs to be
var req = new XMLHttpRequest();.
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