TinEye is a reverse image search engine. Anyone can submit a picture to the website to find out about the image’s origin, the usage of it, if modified versions of it exists, or to find different versions of it with higher resolution.
As claimed by the company, TinEye is the first image search engine website to use image identification technology apart from keywords, metadata and watermarks. Whenever you submit an image to TinEye, it created an unique and compact digital signature or “fingerprint” for it before comparing the fingerprint to all images in their database to find matches. TinEye is able to find a partial fingerprint match. That means, TinEye can find exact matches even for images that have been edited, cropped or resized – it does not only find similar images.
TinEye crawls the web regularly for new images and they also accept contributions of complete online image collections.
TinEye is very useful to find who has stolen your images.
It also has add-on for Firefox, such that you can right click on an image to search for it.
It is free to use for non-commercial purpose.