An EBK file is an eBook file created by eBook Pro, a program used to create eBooks and protect copyrighted information. It stores a compressed and encrypted version of an eBook and can be read using the free eBook Viewer when proper user credentials are supplied.

Publications must be in HTML format before they are converted to an EBK file in eBook Pro. In particular, the publication must include an index.html file in the main source directory. Using eBook Pro, independent publishers and vendors can create their own eBooks. They can also control eBook distribution using the eBook Pro Client Tools program, which allows sellers to manage user access permissions online.