Clara OCR is an Optical Character Recognition program. It features both a powerful GUI for the X Window System, and a Web interface. The Web interface is able to collect revision efforts from the Internet, using a simple revision model. It is intended to be used in the cooperative optical recognition of old books. It tries to facilitate fine- tuning, so an optical recognition project is enabled to invest resources in tuning the OCR, in order to achieve better recognition results for one specific book, and reduce the overall revision cost.