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What is an EPUB File?

How to Open, Edit, & Convert EPUB Files


Question: What is an EPUB File?

Did you find an EPUB file on your computer and wonder what program should open it? Maybe someone emailed you an EPUB file but you're not sure how to use it. Perhaps you tried to open the EPUB file but Windows told you that it could not open it.

Before you can open an EPUB file (assuming it's even a file format that's intended to be viewed or edited), you'll need to determine what kind of file the .EPUB file extension refers to.

Answer: A file with the EPUB file extension is an Open Publication Structure eBook file.

The Open Publication Structure eBook format is a popular and freely available eBook standard so most EPUB files you find will probably be of this format.

Other types of files may also use the EPUB file extension. If you know of any additional file formats that use the .EPUB extension, please let me know so I can update this information.

How To Open an EPUB File

The easiest way to open an EPUB file is to double-click on it and let your PC decide which default application should open the file. If no program opens the EPUB file then you probably don't have an application installed that can view and/or edit EPUB files.

Warning: Take great care when opening executable file formats received via email or downloaded from websites you're not familiar with. See my List of Executable File Extensions for a listing of file extensions to avoid and why.

EPUB files can be opened in most eBook readers, like the B&N Nook and Kobo eReader. EPUB files have to be converted before they're usable on the Amazon Kindle (see How To Convert an EPUB File below).

EPUB files can also be opened on a computer with various free programs including Calibre, Adobe Digital Editions, Stanza Desktop, Mobipocket Reader Desktop, Okular, Sumatra PDF, and many more.

Plenty of iPhone and Android apps also exist that allow viewing of EPUB files. There's even a Firefox Add-on, EPUBReader, that allows you to read EPUB files in the browser just like other documents.

If you know anything else useful about EPUB files, please let me know so I can update this page.

Tip: EPUB files are structured just like ZIP files, meaning that you can rename an EPUB eBook, replacing the .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.

If you find that an application on your PC does try to open the EPUB file but it's the wrong application or if you would rather have another installed program open EPUB files, see my How To Change the Default Program for a Specific File Extension guide for making that change in Windows.

How To Convert an EPUB File

There are three main ways to attempt to convert an EPUB file to another file type:

  • Open the EPUB file in its default program and choose to save the open file as another file format.
  • Download Calibre for free and use it to convert EPUB files to and from other eBook formats, including ones compatible with the Amazon Kindle.
  • Use another File Conversion Online Service or Software Program to convert the EPUB file to another file format.

Most computers don't really have "default" programs for opening or converting EPUB files unless one has been purposefully installed before. In most cases, using Calibre (the second option above) will probably be the solution to any converting you might want to do with EPUB files.

Important: You cannot usually change a file extension (like the EPUB file extension) to one that your computer recognizes and expect the newly renamed file to be usable. An actual file format conversion using one of the methods described above must take place in most cases.

Still Having Problems Opening or Using an EPUB File?

See Get More Help for information about contacting me on social networks or via email, posting on tech support forums, and more. Let me know what kinds of problems you're having with opening or using the EPUB file and I'll see what I can do to help.

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