Chrome: Facebook collects a lot of your data, but you might never get to see what they really learn about you. Data Selfie aims to give you a glimpse by letting you analyse your own Facebook usage.
While there's no way to know exactly how Facebook analyses your data without working for the company, Data Selfie gives you a rough approximation. Once you add it to Chrome, the extension tracks your activity on Facebook. Everything from what you click on to what you type. Data Selfie stores that information locally and doesn't share it with anyone (though obviously Facebook is tracking it).
After a while of usage, you can generate a report that will let you explore what someone could learn about from your activity. It shows simple things like the pages and people you spend the most time with, as well as complex thoughts like how you lean politically, or whether you're more relaxed or emotional.
If you've never paid attention to how simple things like your Facebook activity can turn into powerful data profiles, this is a good tool to play around with. You might think that companies can't know how you lean politically or what your religion is if you don't tell them, but data analysis can figure it out pretty quickly. Whether you're still comfortable using Facebook after seeing reports like the ones Data Selfie generates is up to you, but it's important to know how your data could be used.
Data Selfie [Chrome Web Store]