What Is an EPUB File (and How Do I Open One)?

A file with the .epub file extension is a popular file format used for storing eBooks and other types of content. EPUB, short for electronic publication, was named the official standard of the International Digital Publishing Forum (IDPF) in September 2007.

What Is an EPUB File?

EPUB files can store words, images, stylesheets, fonts, metadata details, and tables of content. They are considered layout agnostic, meaning that screen size doesn’t affect the formatting—EPUB files can display content on screens as small as 3.5″. This and the fact it’s a freely available standard is why a majority of eReaders support EPUB files.

How Do I Open One?

Because of their widespread use, more hardware eReaders support EPUB files than any other eBook file format. You can open an EPUB file whether you’re using a Kobo, Barnes & Noble Nook, or even on your desktop using one of the many free programs, such as Calibre or Stanza Desktop. The notable exception here is Kindle. You cannot read an EPUB file directly on a Kindle, but there are ways to convert one to something the Kindle can use.

iPhone and Android devices come preloaded with their own applications to open eBooks—iBooks and Google Play. If you’re trying to open one on your desktop, you’ll probably want a third-party application.

If you use Windows 10, Microsoft Edge can display EPUB files natively. If Edge isn’t already set up as the default program to handle EPUB files, right-click on the file, point to the “Open With” menu, and then click the “Microsoft Edge” option.

Update: The new, Chromium-based version of Microsoft Edge doesn’t support EPUB files. If you’ve updated, you’ll need a new program to open EPUB files on Windows 10.

Edge will then open up a new tab with your book displayed in the same format it uses for Reader View.

Of course, Edge isn’t going to give you the best reading experience. We’d still recommend using something like Calibre, which can open any number of eBook formats.

How Do I Convert One?

Just like any other file format, you need specialized software to handle converting EPUB into a different format. If you try to change the extension, you could wind up with a corrupt and unusable file.