TinEye is a reverse image search engine that uses image recognition technology to find matching images online. It allows users to upload an image or enter a URL to see where else that image appears online. TinEye has over 1 billion images in its database and is useful for finding copyrighted use of images or locating higher resolution versions. While it is generally free to use, TinEye may eventually charge for its services as it continues to grow its database of images on the web.