Google Analytics was recently updated to change how it calculated when a visitor’s session ended. We were told this should have only a small effect, around 1% on average, on how our visitors were being counted. The change went live on Thursday August 11th. If you look at the graph above you can see on Friday the 12th our reported visits increased by over 40%. This trend continued for nearly a week.
Now a 40% increase in traffic would obviously be welcome, but our unique visitors report told a very different story. Nothing had changed much at all!
So, what was going on? It turns out there were some bugs in the Analytics update that created new sessions for users when they should have had only one. Full details are in the update to the announcement of the original change. It would seem that in our case visitors who clicked the back button in their browser to go back to the landing page they arrived on were being counted multiple times.
Google pushed a fix to this problem on Tuesday the 16th of August and everything seems to be back to normal now, but I’m sure we’re not alone in having spent some time trying to work out what was going on and what changes we’d need to make to be able to compare reports from before and after the change. Thankfully it looks like that’s not an issue anymore. Still, it seems like a pretty big bug to slip through the net for such an important product.