Free optical character recognition engine sponsored by Google since 2006.
Ranked in these QuestionsQuestion Ranking
Pro Support for 40 languages
In the beginning Tesseract only had support English. Now newer versions can support up to 40 languages.
Pro Free and libre software
Pro Works great with 300 DPI files
Pro Very easy to use (see the manual page, not built-in help)
See the manual page.
Pro Can create sandwhich PDF files
Con Rudimentary image processing
Tesseract's image processing is very rudimentary, in order to get the most out of it you need to use a preprocessor or use an image that's already been processed.
A for humans perfectly readable image 100 dpi results in a huge number of failed characters even if source is free from physical scan artifacts (i.e. print to file). If possible, it's better to use 300 dpi image files.
Con Only reads TIFF files
Tesseract can only read TIFF files. If you want to use a picture with a different format (JPEG, PNG, PDF) you need to convert it first.