Feature light Firefox 21 lands

Mozilla has begun shipping out Firefox 21, the latest rapid release of the organisation's flagship web browser. Headlining the release notes is the expanded Social API support. The Social API launched last year with Facebook support allowing the company to create a more integrated sidebar for its services. Now, this is joined by support for Cliqz, Japanese social network Mixi and msnNOW.

There are, though, a few features in this release that will raise issues around ongoing privacy debates. A new interface to Do Not Track (DNT) allows users to now set the DNT flag to "please track" when accessing web sites alongside the previous options of not setting the flag at all or setting it to say "do not track". The default remains to say nothing about the users preferences.

Firefox 21 also sees the first implementation of the Firefox Health Report (FHR) which gathers information about browser stability and performance and sends that data up to Mozilla for further analysis. Mozilla says it will not be collecting IP addresses but will extract country data from them. The statistical data will be held using a rolling document mechanism and the data should always be deleted after 180 days.

FHR should prompt users when Firefox is started after upgrading to Firefox 21 or when it is started for the first time, at which point it can be enabled or disabled. The feature can also be toggled in the preferences under Advanced➤Data Choices, along with the Telemetry and Crash Reporter options. An older FAQ gives more details on this feature. In a slightly, but not directly related feature, if Firefox 21 starts up slowly, it will now make suggestions on how to improve startup time. Among the bug fixes, a problem with function key responses and confusion around clearing of history, after the merge of Browsing and Download history, have been resolved.

Other changes have predominantly been behind the scenes. The History API for add-ons has been tidied up, there's a CSS change to improve WebKit compatibility, E4X (the XML extension for JavaScript) support has been removed from SpiderMonkey and there are some graphics performance improvements.

Developers will find support for remote profiling is now integrated, allowing mobile and desktop web applications to be tested in an isolated browser. The Add-on SDK loader and API libraries have also been built in as the Jetpack project synchronises with Firefox releases. Web designers will find HTML5's <main> is now supported along with an implementation of scoped stylesheets.

Mozilla Firefox 21 will be automatically made available to users of Firefox who have automatic updating enabled. Others can download the release for their current system and browser from the Firefox download page or in any language for Windows, Mac OS X or Linux from Mozilla's Firefox download page. Firefox is licensed under the Mozilla Public License 2.0.

(djwm)