The official date for the launch of Firefox 3.0 is June 17, 2008. Join Firefox set a world record for the most software downloaded in 24 hours. Pledge now. Here are some of the new features of Firefox 3.0. Help spread Firefox. If you want to see a sneak preview of Firefox 3.0, you can download the Release Candidate 3 in your language of choice. Firefox 3.0 is also available in Windows, MacOS and Linux operating systems.