Explaining a Traffic Spike at mozilla.com

Many within the Mozilla community were excited to see this news about the recent surge in traffic at www.mozilla.com.  As great as the recognition is, we’d thought it would be beneficial to take a minute and discuss the exact numbers.  In other words, comScore’s numbers are estimates (based largely on panel data), while internally here at Mozilla, we have the actual numbers from our web analytics solution that are likely more accurate and that we’re happy to share publicly.

Below is a breakdown of all the numbers.  “comScore” refers to the numbers estimated/published by comScore and “Omniture” refers to the web analytics solution deployed internally here at Mozilla.

As comScore’s chairman points out, comScore’s data is immune from issues related to cookie deletion, so one could expect their numbers to be lower than what companies find through their internal data systems. Still – the discrepancy seems far too big to be described by cookie churn.

So, putting aside the discrepancy discussion, what’s the deal with the June to July spike in traffic?

The June to July traffic increase was driven entirely by Firefox releases (e.g.,,, and 3.0.1).  When a release happens, Firefox users automatically see an update page (example here).  If we ignore traffic to these pages during June and July, we see that traffic levels to mozilla.com are virtually identical across months.