Firefox 4 will bring a host of new features, and the first full beta release will showcase the biggest change, a big change to the user interface.
By default tabs will now be at the top of the browser – in a style reminiscent of Opera and Chrome, and will be joined by new features such as a revamped add-on manager, WebM HD video support and privacy improvements.
"Firefox 4 Beta 1 includes dozens of major features and improvements– by testing them early we'll be able to respond to your feedback for future versions of Firefox," blogged Mozilla.
"Once you download Firefox 4 Beta 1, you're part of our beta program and will receive regular updates as more features launch."
Mozilla explained that the decision to move the tabs was based on improving the user experience.
"If you are using a Windows PC, the most noticeable new feature will be the look of the browser.
"We moved the tabs to the top to make it easier to focus on the web content and easier to control the tools in your Web browser.
"Also, if you have Windows 7 or Windows Vista the Menu bar was replaced with a single Firefox button so you can get to the most used options with just one click. These changes will be coming soon for Mac and Linux."
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Patrick Goss is the ex-Editor in Chief of TechRadar. Patrick was a passionate and experienced journalist, and he has been lucky enough to work on some of the finest online properties on the planet, building audiences everywhere and establishing himself at the forefront of digital content. After a long stint as the boss at TechRadar, Patrick has now moved on to a role with Apple, where he is the Managing Editor for the App Store in the UK.