Mozilla Firefox is a fast, light and tidy open source web browser. At its public launch in 2004 Mozilla Firefox was the first browser to challenge Microsoft Internet Explorer’s dominance. Since then, Mozilla Firefox has consistently featured in the top 3 most popular browsers globally. The key features that have made Mozilla Firefox so popular are the simple and effective UI, browser speed and strong security capabilities. The browser is particularly popular with developers thanks to its open source development and active community of advanced users.