EPUB vs MOBI: what's the difference?
EPUB is the open ebook standard used by almost every e-reader and reading app. MOBI is an old Amazon format that Kindle is leaving behind. If you can choose today, choose EPUB, even if you read on a Kindle. Here is how the formats compare, and where AZW3 and KFX fit in.
Quick comparison
| EPUB | MOBI | AZW3 (KF8) | |
|---|---|---|---|
| Made by | Open standard, maintained by the W3C | Mobipocket, bought by Amazon | Amazon |
| Reads on | Kobo, Apple Books, Google Play Books, PocketBook and most apps | Kindles and Kindle apps | Kindles and Kindle apps |
| Styling | Modern HTML and CSS | Very limited | Modern HTML and CSS |
| Send to Kindle | Accepted and converted | No longer accepted | Not accepted; copy it over USB |
| Status | Current standard | Being retired | Still used by Kindle |
What is EPUB?
EPUB is the open format for ebooks, maintained today by the W3C, the body behind web standards. An EPUB file is a ZIP archive of web pages, stylesheets, images and fonts, plus a package file that lists the chapters and the book's metadata.
Most EPUBs are reflowable: the text wraps to fit any screen and the reader chooses the font size. EPUB also has a fixed-layout mode for comics, children's books and anything where every page must look exactly as designed. For the full picture, see how to open EPUB files on each device.
What is MOBI?
MOBI comes from Mobipocket, a company Amazon bought in 2005, and it became the first Kindle format. It is based on old-style HTML, so it supports very little styling: no proper CSS, limited fonts and simple layouts.
Amazon has been retiring it for years. Its KindleGen tool for making MOBI files was discontinued, and since late 2022 Send to Kindle no longer accepts MOBI files. Kindles still open MOBI files that are already on the device, but there is little reason to create new ones.
Where AZW3 and KFX fit in
- AZW3, also called KF8, is Amazon's newer format, introduced in 2011. It supports modern HTML and CSS, much like EPUB. It is the best format to copy to a Kindle over a USB cable.
- KFX is the format Amazon uses for many books bought in the Kindle Store, with improved typesetting. You don't normally create KFX files yourself.
- AZW is essentially a MOBI file with Amazon's DRM. You'll find it in older Kindle Store downloads.
Kobo has its own variant too: KEPUB is an EPUB with extra markup that improves page turning and reading statistics on Kobo devices.
Which format should you use for Kindle?
For most people, EPUB. Send it with Send to Kindle and Amazon converts it for your device, as explained in how to put EPUB books on a Kindle. If you prefer to copy files over a USB cable, convert the EPUB to AZW3 first, for example with the free app Calibre. Only very old Kindles that predate AZW3 still need MOBI.
How to convert MOBI to EPUB
If you have DRM-free MOBI or AZW3 files, convert them to EPUB so they work everywhere, including Send to Kindle. The converter below keeps chapters, images, links and the table of contents, and your file never leaves your device.
Convert MOBI to EPUB, free
Works with MOBI and AZW3 files, right in your browser.
MOBI to EPUB converterFrequently asked questions
Is EPUB better than MOBI?
For almost every use, yes. EPUB supports modern styling, works on nearly every device and is the format Send to Kindle now expects.
Can a Kindle still read MOBI files?
Yes, if the file is already on the device, for example copied over USB. What stopped working is sending MOBI through Send to Kindle.
Will converting MOBI to EPUB lose formatting?
Rarely. MOBI supports so little styling that it converts to EPUB cleanly. AZW3 files keep their stylesheets and embedded fonts.
What is the difference between AZW and AZW3?
AZW is the older, MOBI-based format with Amazon's DRM. AZW3 is the newer KF8 format with modern HTML and CSS.
Related guides
Can Kindle read EPUB?
Three ways to put EPUB books on a Kindle.
EPUB vs PDF
Which format to use, and when.
How to open EPUB files
Free ways to read EPUB on any device.