What is it?
EPUBCheck is a tool to validate the conformance of EPUB publications against the EPUB specifications. EPUBCheck can be run as a standalone command-line tool or used as a Java library.
Basic usage
EPUBCheck is a command line tool. Unzip the file you downloaded and open a terminal program.
Example:
$ java -jar epubcheck.jar moby_dick.epubRead more about the command line interface.