Firefox 4 for desktop launched yesterday and just within 24 hours of being announced, it had been downloaded 7.1 million times.
This is in addition to the more than 3 million people who were already running the release candidate that became a final version, Mozilla said.
According to Mozilla's figures, the downloads of Firefox 4 are more than double those Microsoft had reported
for its Internet Explorer 9 browser, which also launched last week.
includes App Tabs for frequently used applications, a faster engine, do-not-track features and support for HTML5.