The Firefox 4 browser was released Tuesday, March 22, setting up another battle with Internet Explorer for consumer, government and business market share.

Mozilla, the nonprofit developer of Firefox, promises the browser would be up to six times faster than the previous version and support HTML 5, a new JavaScript engine and hardware acceleration. Similar features are also touted by Internet Explorer 9, which was unveiled last week.

Mozilla also announced Firefox 4 would feature “uninterrupted browsing” when the Adobe Flash, Apple QuickTime or Microsoft Silverlight plug-ins crash; a new interface for the browser and tabs; and new security features, including:

  • Do Not Track: A universal standard Firefox is promoting that allows users to opt out of tracking used for behavioral advertising;
  • HTTP Strict Transport Security, which Mozilla says “automatically establishes secure connections to stop ‘man in the middle’ attacks and keep sensitive data safe from interception during the log-in process;” and
  • Content Security Policy, which “prevents cross-scripting attacks by allowing sites to explicitly tell the browser which content is legitimate.”


Firefox 4 had been downloaded 1.2 million times as of Tuesday afternoon.

The release of Firefox 4 comes as many government agencies continue to run older browser versions, potentially making themselves more vulnerable to Web-based cyber-attacks.

Statistics vary about each browser’s market share. Internet Explorer remains the most popular, although the margin isn’t certain. The USA Today cited numbers from Net Applications: 54 percent market share for Internet Explorer, Firefox had almost 18 percent, Google Chrome with 9 percent and Safari at 5 percent. But those numbers will likely change because Internet Explorer doesn’t support Windows XP, the operating system still widely used by many public- and private-sector organizations.