Optical character recognition engine sponsored by Google since 2006.
Ranked in these QuestionsQuestion Ranking
Pro Free, open source and cross-platform
Tesseract is licensed under the Apache with source code available on GitHub. It's available for free on Windows, Linux and OSX.
Pro Understands 40 languages
A full list of languages can be found here.
Pro Can work with custom training data
By inputting custom .traineddata files, Tesseract can adapt to different styles of text accurately.
Pro Multiple front-ends available
Multiple GUIs have been developed for Tesseract, including OCRFeeder.