We’ve heard quite a bit of anecdotal evidence suggesting that Firefox usage saw an upswing in the frequency of crashes during the second half of 2009.  This experience has generally been tied to Firefox 3.5, which was released in late June.  Ideally, we’d have a lot of really rich data to tell a story around the crashiness of Firefox and the associated improvements that are being made.  While some new data systems are about to hit the scene (see here and here) allowing us to figure out precisely what’s going on, we do have a couple data sets that we can rely on today.

Let’s now try to answer the question, “have Firefox users noticed a decrease in the frequency of Firefox crashes during recent months?”

First, let’s look at the total number of crashes.  Below you’ll see a trended ratio that is total daily crashes (i.e., crash report submissions) divided by total active daily users of Firefox.  For example, 1M instances of Firefox crashes in a day divided by 100M users of Firefox on that day would give a ratio of 1%.  It’s a slight trend, but you can see that since early October, the ratio has decreased.  (Please note that this trended ratio assumes a constant client side throttling percentage.)

Next, let’s look at some slightly more qualitative information – the Firefox Uninstall Survey (data is available here).  For the question, “Why did you uninstall Firefox?”, we can see if there’s any trend in the frequency with which people are selecting “Too many crashes” as an response option.  While it is concerning that this option continues to be the #1 reason cited by users, the trend has been in decline since August.

I want to stress that the data points above merely represent some very early analysis – much more is on the way!  That said, the charts above do suggest, at least directionally, that efforts by the Mozilla community (e.g., CrashKill, Socorro team) have been making an impact in recent months.