More than 10% of net users are going online with the Firefox browser, show figures from analysis firm One Stat.
New browsers like Flock are still popping up
The global average of 11.5% is the highest percentage of users that the open source browser has ever reached.
The research also reveals that Americans are the biggest fans of Firefox with 14.1% using it. In the UK 4.9% use it to get around online.
Despite the success, Microsoft's Internet Explorer still dominates the net with an 85.5% market share.
The figures, gathered from a sample of more than two million web users, show that Firefox's market share has grown by almost three percentage points since April 2005.
One Stat said that some of this growth has come at the expense of Microsoft's browser, but it has also stolen users from other browsers such as Opera and Netscape. One Stat also reported that users of Apple's Safari browser for the Mac was also recording good growth figures.
UK BROWSER SHARES
1) Microsoft Internet Explorer - 93.37%
2) Mozilla Firefox - 4.94 %
3) Apple Safari - 0.99 %
4) Opera - 0.39 %
5) Netscape - 0.23 %
It is thought that continuing news stories about security problems in Internet Explorer are helping to fuel the move away from Microsoft's program.
One Stat's figures are at the upper end of all estimates for the success of Firefox. By contrast analysis firm Net Applications gave the browser a 9% market share according to figures gathered in October.
In recent months, browsers, toolbars and the technology around them have become the new front line in the war between the web's biggest companies - Microsoft, Google and Yahoo - to grab and keep hold of users.
New browsers are also continuing to appear. Most recently a browser called Flock launched that tries to make it easier for users to manage what they do on the web, such as remember places of interest and store pictures, in one place.