125 million and one people use Firefox

Mozilla COO John Lilly has revealed statistical data that provides insight into Firefox adoption levels and growth rate. Based on statistics collected internally by Mozilla from the Firefox application update service, Lilly estimates that Firefox is used by over 125 million people around the world. (and one, I too use it)
Firefox market share statistics often attract the interest of technology enthusiasts and market analysts, but they don't always paint a clear picture. Many Firefox market share studies are based on traffic data collected from a broad selection of sites. Lilly comments that studies of that nature can present skewed results depending on the kinds of sites that are incorporated into the research. Sites that are geared towards technology enthusiasts and early adopters, for instance, often have a higher percentage of Firefox users. Lilly also notes that European web sites tend to see more Firefox traffic than sites from the United States, and virtually all of the studies, he argues, undercount browser usage in Asia, South America, and Africa.

"[T]here's no way to really represent the complexity and the dynamism of the global Web—it's just too big, with too many things changing too rapidly," says Lilly. "[A]ll of these studies are extremely useful and help understand what's happening around the world. I'm just asserting that it's very important to understand the limits of particular studies and the assumptions that are baked in."

Lilly also points out that most of the browser market share statistics available from third parties are based mainly on measuring page views rather than users, which he thinks could potentially overstate the extent of Firefox market share. "[M]ost of these measures are in page views, not users," says Lilly in reference to oft-cited third-party browser statistics. "As hard as it is to get an accurate read on worldwide traffic numbers for Firefox, it's even harder to figure out the relationship between page views and users. We have some intuitions here, supported by anecdotal evidence, that Firefox users look at more pages and do more searches than typical users, but nothing that I'd actually call science."

Lilly arrives at the 125 million user estimate by leveraging the statistical data collected by the Firefox application update service. The Firefox web browser sends an anonymous request to the update servers every single day to check for new versions. Counting the total number of pings makes it possible for Mozilla to guess roughly how many instances of Firefox are running on any given day, a metric that Mozilla refers to as Active Daily Users (ADU). This number has climbed from 23 million in October 2006 to 48 million at the high point in November, Lilly says.

Although I don't think that Mozilla's computations based on ADU are significantly more accurate than other browser market share studies, the ADU statistics provide unique insight into several aspects of Firefox usage patterns. The fact that the ADU has doubled since the release of Firefox 2 is a sure sign that Firefox market share is growing rapidly. Although Microsoft is making a strong effort to regain market share, we can probably expect to see a surge in favor of Firefox when Firefox 3 is released next year.


Ryan Paul