Blackout on a sample screenshot.

A sample screenshot with made-up details: a phone number, a card number, an address, an email and a name. Blackout found three of them (the phone number, the card number and the street address) and covered them when we pressed the button. It left the email and the name readable, which is exactly why its own page tells you to look over the whole image yourself before you share it. What else should a tool like this catch?