TinEye: Tracking Your Images, Pixel-By-Pixel

A new image-based search engine can help you see who’s using your images — even if they’ve been cropped, resized, or otherwise altered.

TinEye uses “sophisticated pattern recognition algorithms” to find any instance of an image anywhere on the Internet. As its creators explain it, the service creates “a compact digital signature or ‘fingerprint,'” then compares “its fingerprint to the fingerprint of every single other image in the TinEye search index.”

A complex system, but put simply: You give it an image and it’ll show you who else has it.