Firefox 21 improves performance and privacy

Mozilla has released Firefox 21.0 FINAL, a major new version of its cross-platform, open-source web browser for Windows, Mac and Linux. Version 21 gives users more control over their tracking cookie preferences, extends the social API to support four new providers and implements support for tools to help with troubleshooting and performance issues.

Although Firefox 21 doesn’t have quite the impact version 20 did with its new panel-based downloader, per-window private browsing and ability to close hanging plugins without crashing the entire browser, it still throws in some useful features, all of which have smoothly migrated from the Beta version.

Version 21 builds on Firefox’s Do Not Track feature to provide users with three options via the Privacy tab of Firefox’s Options dialog. The existing "user says nothing" and "user says don’t track" have now been joined by a "Tell sites that I want to be tracked" option for those who actively wish to be tracked in order to see more personally relevant advertising.

Firefox 21 also sees the Social API extended to support new providers. Users can now add Asian social providers Mixi and Weibo, plus news aggregators msnNOW and Cliqz. Once installed, users switch between providers by clicking the main button and selecting the chosen provider from the list.

Also implemented in the latest version is the Firefox Health Report, a tool that provides information designed to improve browser performance while also sharing data with Mozilla regarding the stability and health of the browser installation. The feature is switched on by default, but can be disabled via Firefox’s Options dialog -- select Advanced > Data Choices tab to do so.

At the present time, only preliminary support has been implemented -- users can see information about their own browser stats by selecting Firefox Help Report from the Help menu, but in future this should also allow them to compare their configuration with other Firefox users.

Users also gain an option for restoring removed thumbnails from the New Tab page -- one deleting a thumbnail, a small message briefly appears at the top of the screen allowing the user to undo the action or restore all thumbnails removed previously.

Another improvement sees Firefox monitoring browser start-up times and alerting the user via a Notification bar at the bottom of the screen if startup seems particularly slow -- users can then click a button to visit a web page offering advice for reducing start-up times.

The update also comes with the promise of improved graphics performance, the implementation of Remote Profiling for developers and the removal of support for certain depreciated History APIs as part of Firefox’s drive towards asynchronous History and Bookmarks.

Firefox 21.0 FINAL is available now as a free, open-source download for Windows, Mac and Linux. Beta, Aurora and Nightly channels should be updated later this week.