Amazon deprecated the MOBI format in 2022. Here is everything you need to know about which eBook format to upload to KDP and why EPUB is now the clear choice.
Amazon deprecated MOBI in August 2022. EPUB is now the recommended upload format. Amazon automatically converts your EPUB to KFX for Kindle devices. EPUB also works on every other major platform.
In August 2022, Amazon officially deprecated the MOBI file format for KDP uploads. While the platform still technically accepts MOBI files, Amazon’s own documentation now recommends EPUB as the preferred upload format and states that MOBI no longer provides the same quality conversion benefits that it once did.
MOBI was created by Mobipocket in the early 2000s and acquired by Amazon in 2005. It was designed specifically for e-readers with limited processing power. Over the years, Amazon developed their own superior format called KFX (Kindle Format X), which supports enhanced typography, improved reflowable layout, and better rendering across modern Kindle devices. When you upload EPUB to KDP, Amazon converts it to KFX automatically — and this conversion produces better results than converting from MOBI.
EPUB (Electronic Publication) is an open standard eBook format maintained by the International Digital Publishing Forum (IDPF) and now the W3C. It is the universal standard for eBooks outside of Amazon’s ecosystem and is supported by virtually every major e-reader platform and device: Apple Books, Google Play Books, Kobo, Barnes and Noble Nook, and many others. EPUB uses XHTML and CSS to define content and styling, which makes it highly flexible and compatible.
For KDP authors in 2026, the practical answer is simple: upload EPUB. It produces better Kindle quality than MOBI, it’s the format Amazon officially recommends, and it works on every other publishing platform if you ever want to sell through Apple Books, Kobo, or Google Play Books in addition to Amazon. There is no scenario in which uploading MOBI is the better choice.
| Feature | EPUB | MOBI |
|---|---|---|
| Amazon KDP supported | ✅ Yes (recommended) | ⚠️ Yes (deprecated) |
| Apple Books | ✅ Yes | ✗ No |
| Google Play Books | ✅ Yes | ✗ No |
| Kobo | ✅ Yes | ✗ No |
| KDP conversion quality | ✅ Better (to KFX) | ⚠️ Lower quality |
| Open standard | ✅ Yes | ✗ Amazon-only |
| Recommended in 2026 | ✅ Yes | ✗ No |
Use our free Kindle HTML Converter to generate a clean, semantic HTML file that you can upload directly to KDP or convert to EPUB using Calibre.
Open Kindle Converter →There are several ways to create an EPUB file for uploading to KDP. The simplest is to start with a properly formatted Microsoft Word document (.docx) and let KDP convert it — KDP’s conversion engine handles DOCX well and produces a usable result for most simple manuscripts. However, for more control over the output, creating a proper EPUB is worth the extra effort.
The most popular free tool for EPUB creation is Calibre — a free, open-source eBook management and conversion application. You can import your Word document or HTML file into Calibre and export it as EPUB. The free online tool Sigil allows direct EPUB editing. Vellum (Mac only, paid) is the professional choice for authors who want beautiful EPUB output without technical knowledge.
Before uploading to KDP, validate your EPUB at epubcheck.org — a free validator that checks your file against the EPUB specification and flags any errors that might cause problems during KDP’s conversion process. Fixing validation errors before upload prevents formatting issues in the final Kindle version.
FAQ
Common questions about eBook file formats for Amazon KDP in 2026.
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