What is an ePub file?
ePub is the standard file format for electronic books and publications.
How to open an ePub file
An ePub file opens on a phone, a tablet, an e-reader or a computer. You need a reading app rather than a browser.
On iPhone and iPad, Apple Books opens ePub files directly. On Android, Google Play Books does the same. On Windows and macOS, free desktop readers include Calibre and Thorium Reader.
Web browsers are the common trap. Microsoft Edge could display ePub files on Windows 10 for a while, but Microsoft removed that reader in 2019, and a browser is no longer a reliable way to open one.
Reading ePub on a Kindle
Kindles do not read ePub files from the device’s own storage. Since 2022 you can still get one onto a Kindle: email it to your Send to Kindle address, and Amazon converts it on the way.
This changed the old advice. Amazon used to accept MOBI files through the same service and that is now gone, phased out through late 2023. Sending an ePub is the supported route today, and converting to MOBI first is the wrong way round.
Why ePub text moves around
Like a web page, an ePub is designed to reflow, because that is what it is made of. The text rewraps to the screen it is being read on, and the reader chooses the font and the size.
That is the format’s main strength and its main limitation. For a novel it is exactly right. For anything where the layout carries meaning, such as a comic, a textbook diagram or sheet music, ePub is a poor fit, and a PDF that keeps its fixed page is usually better.
ePub and the other e-book formats
Not every format works on every reader.
ePub and PDF are the two you meet most often, and almost every device handles both. Kindles are the exception on ePub: they use Amazon’s own formats, AZW3 and KFX, with MOBI surviving only as a legacy format on older files.
Apple once had its own IBA format, produced by iBooks Author. Apple discontinued that app in July 2020 and folded book creation into Pages, so IBA is now something you might inherit rather than something you would choose.
Converting an ePub file
Calibre is the usual answer. It is free, it runs on Windows, macOS and Linux, it reads ePub files, and it converts between formats.
Calibre: calibre-ebook.com
Online converters exist and are convenient for a single file, though you are uploading the book to somebody else’s server, which is worth a thought if the file is not yours to share.
If you are preparing a book for Kindle rather than just reading one, Amazon’s free Kindle Previewer shows how an ePub will look on different Kindle models before you publish it.
Kindle Previewer: kdp.amazon.com
Reviewed September 2026. The Kindle and Apple details above changed after this article was first written in 2021: Amazon ended MOBI support in Send to Kindle, Microsoft removed the ePub reader from Edge, and Apple discontinued iBooks Author.