The news: Facebook has launched its “Off-Facebook Activity” tool, which lets users manage and delete the data that third-party apps and websites share with Facebook. It was originally called the “Clear History” button when it was announced in 2018, as the company came under fire for sharing millions of Americans’ personal data with political consultancy Cambridge Analytica.

A nasty shock: It’s worth going and seeing for yourself just how much data about you is being shared with Facebook. Here’s how to do it. I counted a grand total of 812 apps and websites sending data about me back to Facebook, from national newspapers to my local coffee shop. At this point, it feels safe to assume that most of the websites I’m visiting or apps I’m signing up to are probably sharing data on me with Facebook.

Not what it seems: Naturally, I pressed the button to clear the data from my account. But it’s a bit misleading—Facebook isn’t deleting any data from third-parties, it’s just de-linking it from its own data on you. It also doesn’t stop the third parties from sharing data with Facebook in the future. You have to go to a different section of your Facebook settings to do that.

The ugly truth: It feels deeply uncomfortable to see your data history laid out like this, but this sort of tracking across platforms isn’t exceptional. It’s how the advertising technology industry works. Whether it’s legal is another question.

Sign up here to our daily newsletter The Download to get your dose of the latest must-read news from the world of emerging tech.