How people use private browsing

Private browsing. All the modern browsers have it. Turn it on, and the browser won’t keep your history during the session. Sometimes it’s used to pay bank bills on a public computer. Sometimes it’s used for other stuff. In an opt-in study looking at a week in the life of a browser, Mozilla looked at how people use private browsing.

Again, it’s worth noting that people opted in to this study (about 4,000 of them), and Mozilla only recorded when users started and stopped private browsing. Nothing in between.

That said, they came up with two basic findings. The first is when people typically use private browsing (above).

They saw usage spikes during the lunch hours as well as just before the work day ended. The other spike is after the dinner hours and then finally, in the late hours of the night.

The second observation was that most people go into private browsing for somewhere in the ten minutes range:

This is interesting and all, but what do we really want to know? What’re people doing during those spikes? Of course, that data doesn’t exist, and if it did, that’d be some serious privacy stuff. So instead, all we can do is speculate. Leave your guess in the comments below.

There’s some aggregated data available from the study, but I don’t see any raw anonymized data or anything pertaining to private browsing.



  • I know exactly what they are doing: their own bloody business ;)

  • The other matter is that most people do their browsing (private or otherwise) at lunch time so any conclusions about the prevalence of private browsing need to be taken in the context of how many people are browsing anyway.

  • Oh, plus the relatively small sample group could be different from the general Firefox-using population.

  • I wonder how usage compares to Incognito mode usage in Chrome. I eagerly await Google’s response…

  • Ok i’ll be the one naming the elephant in the room. Its porn, most of it. if you disagree then you are in denial.

    • So all we need is traffic data for a porn site. The hourly traffic should match with the hourly private mode usage. Okay, who knows a porn webmaster?

  • Gerard St. Croix August 25, 2010 at 1:58 am

    Not hardly. The intersection between the populations who understand why they should be using privacy mode to begin with and the populations who don’t understand that everything they do is still passed on and logged by the corporate network has to be minuscule.

    My guess would be accessing private email, social networking sites, private banking and personal interest forums that you don’t necessarily want to share with everybody who happens by, but that wouldn’t be socially and professionally embarrassing if it were discovered, provided you can make the case it only happens during your off-time.

    Durations and times seem to bear that out.

  • I would love to know how many of the people in the study actually believe that their sessions are truly private when in private mode? The private browsing option turns off local history logging, but your visits can still be recorded easily.
    Government, financial, insurance and some even smaller companies log this data, outside the local PC.

  • it’s PORN. this is not rocket science.

  • My hunch is that some of the private browsing activity done during the lunch hour has to do with looking up health-related information.

  • In privte browsing,Private? Give me a break, nothing is “Private” on a computer