You Can Use Facebook To Check When Your Friends Wake Up

In an interesting article on Medium, Søren Louv-Jansen has revealed how one can use a little snippet of code on Facebook’s Messenger site to track a friend’s sleeping habits. While Facebook keeps track of every time you visit the website, the Facebook app, or the Messenger app, it’s creepy to find out that your friends can easily get access to this information as well.

As the author points out, the web-based Facebook Messenger can tell you when a user was last active (as shown above). Curious to find out where this data was coming from, he did some digging and found a list of user IDs and timestamps of their last activity (shown below).

The above can be loosely translated to:

— Peter was last active on Feb 21 2016 15:34:25

— John Doe was last active on Feb 21 2016 17:15:11

— Elizabeth was last active on Feb 21 2016 10:09:55

.…and so forth

By creating a simple service that checks Facebook every 10 minutes, I’m able to get an accurate picture of my friends’ Facebook usage. Many people visit Facebook as the first thing in the morning, and the last thing before going to bed. It is therefore possible to get a good impression of their sleeping habits (or lack thereof).

The sleeping habits derived from Facebook activity. This person has a fairly stable circadian rhythms, going to bed around 11PM and getting up around 6.30AM

The author has already published the source code on Github. By cloning it, you can run the service locally, and you will start seeing the sleeping patterns of your friends. Check out the following video to see it in action:

Moral of the story: We cannot hide
Everybody I’ve shown this to have been equally fascinated and outraged by the accuracy with which it predicts their sleep habits. In this digital world we leave footprints where we go, and when we do it, without even thinking about it. Facebook might block this little “hack”, so your friends no longer can track you, but Facebook will always be able to do their own data analysis which is undoubtably way better than what I’ve come up with. They are likely using this data for profiling, and creating more user-specific ads.