"Mozilla created 'do not track' to give users more control over the way their browsing behaviour is tracked and used on the web. The feature, which lets users tell websites that they wish to opt-out of online behavioural tracking, is now easier to find in Firefox Preferences," said Mozilla in a blog post.
"The latest version of Firefox includes more than 1,000 improvements and performance enhancements that make it easier to discover and use all of the innovative features in Firefox," added Mozilla.
The company said its shift to a rapid release development cycle makes it easier for developers to build Firefox add-ons and means new Firefox features, security updates and enhancements are delivered to users faster.
Firefox 4 had more than 200 million downloads on Windows, Mac and Linux.
To download Firefox 5, click "check for update" in the "About Firefox" menu, or download the Firefox Aurora and Beta channels here.
Android users will receive a notification to update to the latest version of Firefox.
Read the technical release notes here.