What Is an EPUB File?

EPUB is the most popular file format for digital books

What to Know

This article explains what an EPUB file is, how to open one on all your devices, and how to convert one to a different format that will work with your eReader.

What Is an EPUB File?

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

EPUB 3.2 is the latest EPUB version. It supports the latest versions of HTML, CSS, and SVG, and has built-in support for embedded interactivity, audio, and video.

EPUB Files

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 eBook 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 Readium.

Plenty of iPhone and Android apps view EPUB files. There are also add-ons and extensions for Firefox and Chrome that let you read EPUB files in the browser just like other documents. EPUBReader for Firefox and Simple EPUB Reader for Chrome are just a couple examples.

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 eBook, 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 eBook 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 GIF, PNG, JPG, and SVG images.

How to Convert an EPUB File

There are several ways to convert EPUB files:

  • Calibre is the premier program for converting an EPUB file to another format. It converts to and from most other eBook 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.
  • 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.
  • Using the Online eBook Converter is one way to make an EPUB file from another document file like AZW or PDF.

You can try to convert an EPUB file by opening it in one of the other eBook 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 Open eBook files, they're used by Microsoft's Publisher as Publisher Document files.

It's also easy to confuse an EPM or EBM file for an EPUB file. EBM files are either EXTRA! Basic Macro files or Embla Recording files, but neither format is an eBook. 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.