Guide
AZW3 vs EPUB: the Kindle format against the open one
AZW3 vs EPUB is mostly a question of where you read. AZW3 is Amazon's own Kindle format, so it's the file to copy to a Kindle over USB. EPUB is the open standard that everything else reads. Inside, the two are close, so a DRM-free book moves between them with nothing lost.
AZW3, also called KF8 or Kindle Format 8, replaced MOBI on Kindles and is built on modern web markup, much like EPUB. That's why this comparison is closer than people expect, and our test shows it.
Where each one works
| AZW3 | EPUB | |
|---|---|---|
| Kindle, copied by USB | Yes | No |
| Kindle, by Send to Kindle | No | Yes, converted on delivery |
| Kindle app on a phone or tablet | Store books and sent documents only | Through Send to Kindle |
| Apple Books, Google Play Books, Kobo, Nook | No | Yes |
| Owner of the format | Amazon | Open standard (W3C) |
| Fonts, styling, contents list | Yes | Yes |
Going from one to the other: what we measured
We converted Project Gutenberg's AZW3 files of Alice's Adventures in Wonderland and The Adventures of Sherlock Holmes to EPUB with seven converters in November 2026, and went the other way with our own converter.
- The text survives both ways. AZW3 to EPUB kept 100% of the words on all seven converters, and so did EPUB to AZW3 on the two books we tried.
- So does the structure. Contents lists, chapter headings, title, author and cover all came through whole. That's a real contrast with old MOBI files.
- The files are close in size. Alice is 185 KB as an EPUB and 249 KB as an AZW3.
- The EPUB standard is stricter than a Kindle. EPUBs from the other six converters failed EPUBCheck, the official validator, with 114 to 124 errors across the two books. A reading app may not mind, but strict readers and stores can refuse such a file. Ours passed with none.
The full table is on the AZW3 to EPUB converter page.
Which to keep
Keep EPUB as your main copy. It's the one you'll still be able to open on whatever you read on in
ten years, and it reaches a Kindle anyway. Make an AZW3 only for a Kindle that stays offline, with
the EPUB to AZW3 converter: connect the Kindle by USB and drop the file in its
documents folder. If you already have a DRM-free AZW3 and want it on a Kobo, a phone or Apple Books,
convert it to EPUB. For printing, AZW3 to PDF is the route.
One limit applies to every tool: Kindle store purchases are protected by DRM and can't be converted. Files that work are ones you made yourself, or that came DRM-free from a library, an author or a shop such as Project Gutenberg.
Questions
How can I convert an AZW3 file to an EPUB file?
Upload it to our AZW3 to EPUB converter and download the EPUB. This works for DRM-free files; Kindle store books are protected and can't be converted.
Is AZW3 better than EPUB?
Only on a Kindle over USB. The two hold the same kinds of content, and in our test no words were lost in either direction, but only EPUB opens outside Amazon's world.
What is the EPUB 3 format?
EPUB 3 is the current version of the standard, built on HTML5, with better support for audio, maths and accessibility. Our converters write EPUB 3 and keep the older contents file so that older e-readers still work.
How do I put an AZW3 file on a Kindle?
Connect the Kindle to a computer by USB and copy the file into its documents folder. It then shows up in your library.
Kindle and Send to Kindle are trademarks of Amazon.com, Inc. epubwise is not affiliated with Amazon.