There have been two side effects of our recent changes to tracking that we didn’t really anticipate. This doesn’t mean that something is broken, things just work differently now. We wanted to post about them here so you can understand what’s going on.

More visitors / less actions per visit

You may have seen your daily visitor account increase substantially, but the number of actions remains the same. The main types of sites that are seeing this are those that have user accounts (e.g. people login to your site to do whatever it is they do on it).

What’s happening here? First, people tend to share their accounts with other people. We are seeing this big time on in our stats for, for example. We see multiple sessions from the same user account and the same IP address at around the same time, which previously would have been counted as the same session. Because we have cookies now, we are able to determine that these are in fact two unique users. We can tell because when we view these sessions, in almost all cases the computer details are different. One might have Windows XP and Firefox 3.0, the other Windows Vista and Internet Explorer. Since the old method was just using the IP address, they would have been clumped together into one visit. The new system seperates them into two unique sessions, as they should be, since they are occurring on two different computers.

What about the other cases? Well, the same thing can also happen for one visitor using two different browsers on one computer to access our site. Since cookies are stored at the browser level, their cookie ID will be different in each browser used. This isn’t really desirable here, but it’s also quite rare. Not many people use multiple browsers at the same time. All other analytics services that use cookies will have the same problem. If you think about it though, it really is two different sessions, because the person is doing two seperate things in the two browsers.

“Visitors online” in Spy is lower

If you have a moderate traffic site (at least ~5,000 daily visitors), you may have noticed that when you load up Spy, the “visitors online” value is quite a bit lower than the one you see reported on the dashboard.

The reason this is happening is because we only store the last X number of actions in the Spy “cache” for each site. Although we don’t count pings as “actions” in your stats, the way that they are processed in the backend is the same. Since pings are now stored in that cache, when you first load Spy, the cache may not actually have all of the data for your visitors that are all online at that moment. So you will see lower number initially, but once Spy has been running for a few minutes, it should have a much more accurate number. We want to fix this and will probably increase the size of the cache, but we need to be careful about doing that.

You also may be seeing lower numbers because you don’t actually have as many visitors online at one time. As we explained in our last post, Spy now uses the pings to determine when visitors are truly online or not, rather than a generic 5 minute timeout that we were doing before. Now Spy will know within 1 minute of a visitor leaving your site that they have actually left (because the pings have stopped), instead of waiting 5 minutes to remove them. The end result here is that we remove visitors a lot quicker from Spy than we used to, so the value we report here might be lower than it used to be. But it’s more accurate, and that’s a good thing.

Hope that helps.