Firefox growth rate slips again

The Firefox browser continues to rack up incremental market share gains against Microsoft's Internet Explorer, but security concerns may be taking their toll as the growth rate continues to slip.

Website measurement and marketing firm WebSideStory said that as of April 29, IE fell a percentage point in domestic share to make up 88.9 per cent of browser usage, while the Mozilla Foundation's open-source Firefox browser rose just over a point to 6.8 per cent.

The single-point gain represents a second consecutive slowdown for Firefox. While the browser gained a half point of market share per month in the period after its test launch in June, and a whole point per month in the period after its 1.0 launch in November, it's now gaining just over one-third of a point per month.

WebSideStory analyst Geoff Johnston said: "The pace has slowed down again. We started to notice that trend in the last release."

The slackening of Firefox's growth could mean that the browser has converted a substantial proportion of its natural constituency, thought to be early adopters and the technically savvy. It could also show that the browser's widely publicised security flaws have begun to undermine the foundation's argument that people should switch from IE to be safer.

The Mozilla Foundation warned against assigning too much importance to falling growth rates, and said the Firefox security profile still bested the competition.

Chris Hofmann, Mozilla's director of engineering, said: "We've had a few security updates, but they've been for potential vulnerabilities, for staying ahead of the curve of potential problems that might come down the road. You don't have widespread reports that people are being exploited when they use Firefox. I'm not sure there's any evidence that people are migrating away from Firefox because they feel less secure."

On the contrary, Hofmann said, Mozilla has earned kudos from security-minded users for quickly turning around patches before holes are manifested in actual exploits.

Whatever its cause, the growth slowdown calls into question the viability of one of Mozilla's stated goals for the year: topping 10 per cent market share.

WebSideStory's Johnston said that Firefox could not allow its growth rate to fall any further if it expected to achieve that goal.

"It's going to take no erosion and maybe a little bit of an uptick to surpass that by the end of the year," said Johnston. "It may depend on what they come up with in a new version this summer."

Hofmann called the 10 per cent goal "aggressive" and said the foundation was doing what it could in terms of distribution deals and marketing campaigns.

Even as its numbers painted a troubling picture for Firefox's growth, WebSideStory called attention to the browser's overall success in penetrating the IE juggernaut.

The slowdown "can be looked at in a couple of ways", Johnston said. "One is that Firefox adoption is starting to slow, and another is that it continues to plug ahead. Last June, I would never have thought that Firefox would keep growing for a full year, because Microsoft had never moved backwards."

Late last month Firefox marked 50 million downloads of its browser since the Version 1.0 release in November.

Paul Festa writes for CNET News.com