While we still don't know for certain just what it is that people look at when they switch Firefox to the "private browsing" mode, we do now know when they're most likely to use it—and for how long.
Based on an opt-in test pilot study conducted by Mozilla, there is a pattern to when people seek out some quiet alone time with their browsers:
Though people switch into Private Browsing mode throughout the day, there are a few periods where activation surges:
- Lunch: users likely switch into Private Browsing during their lunch breaks. We see a major spike between 11 and 2pm.
- After School / Work: users appear to switch on Private Browsing just after they've returned from work or school, which is around 5pm.
- After Dinner: we have another substantial peak between nine and ten pm.
- Late Night: a minor spike exists an hour or two after midnight.
The folks at Mozilla were also able to determine for just how long people leave their browsers in private browsing mode:
The 25th percentile stays on for about 4 and a half minutes, the 75th percentile around 22 minutes, and the median stays in for about 10 minutes.
This trend appears to hold over the entire course of the day, with the notable exception of 5pm. For some reason the median and lower quantiles are lower than the other hours.
As far as what goes on during these rather consistent private browsing sessions, Mozilla would only say that "what happens in Private Browsing stays in Private Private Browsing." [Mozilla via Mashable]