What is an ePub file?

EPUB is a file format for e-books. It is used by the popular EPUB reader apps and e-book readers, Amazon Kindle, Barnes & Noble Nook, Google Play Books, Kobo eReader, and Apple iBooks.

The EPUB file format was developed by the International Digital Publishing Forum (IDPF), a non-profit trade association that includes major publishers such as Random House and HarperCollins.[1] It was designed to be an open standard format, which could be used to produce electronic books that look good on a wide variety of devices. The first version of EPUB was published in 2004.