Guide
EPUB vs MOBI: why EPUB won, and when MOBI still matters
In EPUB vs MOBI, EPUB is the one to use today: it's an open standard that nearly every reading app opens, and Amazon's Send to Kindle now takes it. MOBI is an old Kindle-era format, worth keeping only for files you already own, and those are easy to convert.
MOBI started as the Mobipocket format, which Amazon bought in 2005 and built the first Kindles on. EPUB grew up as the shared standard for everyone else. Here's what that history means for a file you have today, with numbers from eight converters.
The practical differences
| EPUB | MOBI | |
|---|---|---|
| Who controls it | Open standard (W3C) | Amazon, no longer developed |
| Apple Books, Google Play Books, Kobo, Nook | Yes | No, or only through a side app |
| Send to Kindle | Accepted | No longer listed |
| Copying to a Kindle over USB | No | Yes, on Kindles that still read it |
| Styling and pictures | Modern web styling | Basic |
| Screen readers | Real headings and reading order | Often just big bold text |
What's inside an old MOBI: our test
We ran Project Gutenberg's MOBI of Moby-Dick and of Alice's Adventures in Wonderland through eight converters in November 2026 and read the results with one script. Two findings explain why MOBI ages badly.
Chapters aren't really marked. Moby-Dick has 145 entries in its contents, yet in the MOBI each chapter title is only large bold text. Five of the seven other converters carried across none of them as real headings and the other two just one, so a reading app or screen reader can't tell where a chapter begins. We convert all 145.
The markup is out of date. A straight conversion to EPUB failed EPUBCheck, the official validator, with 272 to 372 errors across the two books, because MOBI's old HTML isn't allowed in an EPUB. Our cleaned-up files had none. The words themselves were fine in every case: all the converters kept the text of Alice, at 99.8% or more.
So nothing is lost in moving away from MOBI, and a careful conversion leaves the book in better shape than it started. The full table is on the MOBI to EPUB converter page.
What to do with your files
- You have a .mobi: keep the original and convert it to EPUB. It then opens almost anywhere, and it can go to a Kindle through Send to Kindle.
- You're reading on a recent Kindle: send it the EPUB. Amazon converts it on delivery, so you don't need a MOBI first.
- Your Kindle never goes online: copy a file over USB. Use AZW3 if the device reads it; AZW3 vs EPUB explains the difference. Only make a MOBI for a very old model.
- You want it printed: a PDF is one conversion away, and EPUB vs PDF covers when that's the better choice.
All of this applies to DRM-free files. A book bought from the Kindle store is locked to your Amazon account, and converters, including this one, can't open it.
Questions
Is EPUB the best format for Kindle?
It's the one to send. Send to Kindle takes EPUB and converts it on delivery, and no longer lists MOBI. For a Kindle that stays offline, copy an AZW3 file over USB.
Is MOBI obsolete?
For new books, yes. Amazon has moved on to newer Kindle formats and EPUB uploads. Old MOBI files still open on many Kindles, but most other reading apps don't read them, so converting yours is sensible.
What type of file does Kindle use for ebooks?
Kindle store books use Amazon's own formats, such as AZW3 and KFX. Files you send yourself usually start as EPUB, PDF or Word documents.
Do I lose anything converting MOBI to EPUB?
Not the words: every converter we tested kept the text of Alice at 99.8% or more. Chapter headings and clean markup depend on the converter, which is what our table shows.
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