If you are publishing a new Kindle book, you generally do not need to convert your EPUB to MOBI. Amazon stopped accepting MOBI for reflowable books in 2021 and for fixed-layout books in March 2025. Modern Kindle publishing uses EPUB and Amazon's other current manuscript formats, and the EPUB you build for Apple or Kobo is the same one you upload to KDP.
That is the whole answer. The rest of this page is for anyone who found it by searching "EPUB to MOBI" and wants to know why the advice they were following is out of date.
| EPUB | MOBI | |
|---|---|---|
| What it is | The open ebook standard, published by the W3C | Amazon's old proprietary format, inherited from Mobipocket |
| Status | Current — EPUB 3.3 is a W3C Recommendation | Retired for KDP uploads |
| Accepted by KDP | Yes | No, since 2021 (reflowable) and March 2025 (fixed layout) |
| Accepted elsewhere | Apple Books, Kobo, Google Play, libraries — everywhere | Nowhere |
| Build it for a new book | Yes | No |
What MOBI was
MOBI was the file format of Mobipocket, a French ebook company Amazon bought in 2005. When the first Kindle shipped two years later, it read a variant of that format, and for a long stretch "make a Kindle book" meant "make a MOBI" — usually by running an EPUB through a converter such as KindleGen or Calibre.
That history is why the advice persists. A decade of blog posts, forum threads and how-to guides told authors to convert EPUB to MOBI before uploading, and those pages are still ranking. They were right when they were written.
What happened to it
Amazon moved on internally first. Newer Kindles stopped storing books as MOBI years ago in favour of Amazon's own later formats — AZW3, and then KFX — and what a Kindle holds today is neither MOBI nor EPUB but whatever Amazon converts your upload into.
Then Amazon stopped taking MOBI at the door. Reflowable books first, in 2021. Fixed-layout books — picture books, comics — followed in March 2025, which closed the last route. Its current list of accepted ebook manuscript formats, cited at the foot of this page, does not include it.
Neither event was dramatic. Uploading an EPUB had been possible, and better, for years; MOBI simply outlived its purpose and was retired.
What to upload instead
For a reflowable book — a novel, a memoir, anything that is mostly words — KDP accepts EPUB, Word (DOC or DOCX), KPF from Kindle Create, HTML, RTF and plain text. Kindle file formats walks through all of them.
Of those, EPUB is the one to build if you want control over the chapter navigation and the metadata, or if you are publishing anywhere other than Amazon. It is the same file everywhere: one validated EPUB 3 uploads to KDP, Apple Books, Kobo and Google Play without a separate conversion for each. Kindle: EPUB or Word? is the decision between the two realistic options.
The one case you might still meet a MOBI
Advance reader copies. Some authors still send a MOBI to reviewers with older Kindles, and some formatting tools still offer a MOBI export for exactly that. It is a distribution convenience for a handful of readers, not a publishing format, and the same reviewers can be sent the EPUB — every Kindle made in the last several years opens one through Send to Kindle.
If you already have a MOBI and nothing else, the practical route is to convert it back to EPUB, check that with EPUBCheck, and go forward from there. Calibre will do the conversion. What it cannot do is recover structure that the MOBI never had, so look at the chapter menu in the result before you trust it.
The short version
- New book? Build an EPUB. Do not convert it to MOBI; KDP will not take one.
- Old guide says "convert to MOBI"? It was written before 2021. The rest of its advice may be equally dated.
- Have a MOBI and nothing else? Convert it to EPUB, validate, and check the navigation survived.