What Is an EPUB File?

EPUB is the most popular file format for digital books

EPUB files in Windows 10
EPUB Files.

 Tim Fisher


The EPUB file format (short for electronic publication) is an e-book format with the extension .epub. You can download EPUB files and read them on your smartphone, tablet, e-reader, or computer. This freely available e-book standard supports more hardware e-book readers than any other file format.

EPUB 3.1 is the latest EPUB version. It supports embedded interactivity, audio, and video.

If you're looking for free EPUB book downloads, know that there are lots of online resources where you can find free books, such as Open Library.

How to Open an EPUB File

EPUB files can be opened in most e-book readers, including the B&N NookKobo eReader, and Apple's Books app. EPUB files have to be converted before they're usable on the Amazon Kindle.

EPUB files can also be opened on a computer with several free programs, such as Calibre, Adobe Digital Editions, Apple BooksEPUB File Reader, Stanza Desktop, Okular, and Sumatra PDF.

In addition to a few of the programs just mentioned, Mac users can read EPUB files with Kitabu.

If you have Windows 10, the default, built-in browser called Microsoft Edge features out-of-the-box support for reading EPUB files — no additional software necessary.

Plenty of iPhone and Android apps view EPUB files. There's even a Firefox Add-on (EPUBReader) and Chrome app (Simple EPUB Reader) that allow you to read EPUB files in the browser just like other documents.

Google Play Books is another place you can open EPUB files by uploading the EPUB file to your Google account and viewing it through the web client.

Since EPUB files are structured like ZIP files, you can rename an EPUB e-book, replacing .epub with .zip, and then open the file with your favorite file compression program, like the free 7-Zip tool. Inside you should find the contents of the EPUB e-book in HTML format, as well as the images and styles used to create the EPUB file. The EPUB file format supports embedding files such as GIFPNGJPG, and SVG images.

How to Convert an EPUB File

Methods for converting EPUB files include:

  • Calibre is the premier program for converting an EPUB file to another format. It converts to and from most other e-book formats, including ones compatible with the Amazon Kindle. Some of the supported conversions include EPUB to FB2, HTML, LIT, LRF, MOBI, PDF, PDB, RTF, TXT, and SNB.
  • Using the Online eBook Converter is another way to quickly create an EPUB file from another format such as AZW, TCR, and others, through an online conversion service. The site also has ePub Converter so that you can convert other file types, such as PDF, to the EPUB format. This is a super-simple way to create an e-book from your original document file.
  • Zamzar is another online EPUB converter worth mentioning. You can use the website to convert the EPUB file to PDF, TXT, FB2, and other similar text formats.

You can try to convert an EPUB file by opening it in one of the other e-book readers and choosing to save or export the open file as another file format, although this is probably not as effective as using Calibre or the online converters.

If none of those methods work, check out other file conversion software programs.

Still Can't Open the File?

One of the most common mistakes when opening an unfamiliar file type is misreading the file extension. Although different file formats use different file extensions, they sometimes look an awful lot alike, which can be confusing when trying to open or convert one.

For example, a PUB file is only one letter away from using the exact same suffix as EPUB files, but instead of being electronic publication files, they're used by Microsoft's Publisher as Publisher Document files.

It's also easy to confuse an EBM file for an EPUB file. EBM files are either EXTRA! Basic Macro files or Embla Recording files, but neither format is an e-book. The first opens with Micro Focus software and the other is used by Embla RemLogic software.

If you discover that your file actually isn't using the EPUB file extension, re-read it to see what the extension is and then research it on Google or here on Lifewire to learn more about what it's used for and how to open and/or convert it.