Firefox, which the Mozilla Foundation released in version 1.0 in early November, has seen its US growth rate for actual usage fall by nearly half since its debut, according to WebSideStory, a Web analytics company.
The browser's market share grew by 15 percent in a five-week period leading up to February 18, compared with a 34 percent increase within the same timeframe after its debut, according to the study.
"This is probably to be expected as we move beyond the early adopter segment," Jeff Lunsford, WebSideStory's chief executive, said in a statement.
The statistics are based on the number of users who have not only downloaded the browser but who have installed it and are using it to view Web sites that WebSideStory tracks. According to the Mozilla Foundation, 25 million copies of Firefox have been downloaded in the past 100 days.
Since its debut, Firefox has grabbed nearly 5.7 percent of the US market share for browsers. Microsoft's Internet Explorer, meanwhile, has seen its market share fall to 89.9 percent -- down three percentage points -- in that time.
"In December, it seemed Firefox was a lock to reach 10 percent (market share) by mid-2005, ahead of the reported year-end goal of the Mozilla Foundation," Lunsford said. "Given the latest growth rates, the year-end target still appears attainable, but a midyear achievement is unlikely."
Nonetheless, the interest of Firefox has been substantial. The Mozilla Foundation, for example, raised more than US$250,000 in the first 10 days of a fundraising campaign, which it used to place full-page ads in The New York Times to herald the debut of Firefox 1.0.
