EpubCheck is a tool to validate EPUB files. It is also able to extract technical characteristics and embedded metadata from an EPUB file. Both the EPUB 2 and EPUB 3 formats are supported. EpubCheck can be run as a standalone command-line tool or used as a Java library. Development of this tool is supported by the International Digital Publishing Forum (IDPF), which also publishes the EPUB standards.
Online version of EpubCheck