Last reviewed by The publishing.co.uk Team — May 2026
Amazon deprecated the MOBI format in August 2022. If you are publishing a Kindle eBook in 2026, here is everything you need to know about which format to upload.
UK note: UK-specific considerations apply — ISBN purchases go through Nielsen (not Bowker), VAT rules differ from the US (print books are zero-rated; ebooks carry 20% VAT), and GDPR applies to any email/customer data. See our UK self-publishing guides for specifics.
At publishing.co.uk we work with UK indie authors across every stage, so this guide reflects what we've actually seen succeed (and fail) rather than recycled advice.
The Quick Answer
In 2026, upload EPUB to Amazon KDP
EPUB is the clear winner
MOBI has been deprecated since August 2022. Amazon now converts all uploads to their internal KF8 format, and EPUB produces the best results.
Format Status in 2026
EPUB
Industry standard. Best feature support. Works on all platforms. Smallest file sizes.
KPF / DOCX
KPF from Kindle Create. DOCX accepted but may have formatting issues.
MOBI
No longer accepted for upload since August 2022. Cannot be used for new publications.
Which Format Should I Use? (Decision Tree)
Upload EPUB
EPUB is the best choice for your situation. It offers the widest feature support, smallest file sizes, and works across all platforms including Amazon KDP.
Consider KPF (Kindle Package Format)
For complex layouts on Amazon only, Kindle Create can produce a KPF file that preserves your formatting. However, EPUB is still the more versatile choice.
Definitely use EPUB
Since you are publishing on multiple platforms, EPUB is essential. It is the universal eBook standard accepted by Apple Books, Kobo, Google Play, and Amazon KDP.
Side-by-Side Feature Comparison
| Feature | EPUB | MOBI | KPF |
|---|---|---|---|
| KDP Upload Status | Accepted ✓ | Deprecated ✗ | Accepted ✓ |
| Multi-Platform | All platforms ✓ | Amazon only ✗ | Amazon only ✗ |
| Reflowable Text | Full support ✓ | Supported ✓ | Supported ✓ |
| Fixed Layout | Full support ✓ | Limited ⚠ | Full support ✓ |
| Embedded Fonts | Full support ✓ | Not supported ✗ | Supported ✓ |
| Audio/Video | EPUB3 support ✓ | Not supported ✗ | Limited ⚠ |
| CSS Styling | Full CSS3 ✓ | Limited CSS ⚠ | Full CSS ✓ |
| SVG Images | Supported ✓ | Not supported ✗ | Limited ⚠ |
| Accessibility | WCAG compliant ✓ | Limited ✗ | Partial ⚠ |
| Typical File Size | Small (1-5 MB) | Large (3-15 MB) | Medium (2-8 MB) |
| DRM Support | Supported ✓ | Supported ✓ | Supported ✓ |
| Open Standard | Yes (W3C) ✓ | Proprietary ✗ | Proprietary ✗ |
Timeline: The End of MOBI
| Date | Event |
|---|---|
| 2007 | Amazon acquires Mobipocket, uses MOBI as Kindle format |
| 2011 | Amazon introduces KF8 format alongside MOBI |
| 2018 | Amazon begins accepting EPUB uploads |
| August 2022 | Amazon officially deprecates MOBI — no longer accepted for upload |
| 2023 | Amazon's "Send to Kindle" stops supporting MOBI |
| 2026 | EPUB is the universal standard; MOBI is obsolete |
How to Convert MOBI to EPUB
If you have existing MOBI files, here is how to convert them:
- Calibre (free) — Download from calibre-ebook.com, import your MOBI, and convert to EPUB
- Original source — If you have the original Word/InDesign file, export directly as EPUB
- Professional conversion — For complex books, a professional conversion ensures no formatting is lost
Need a Kindle EPUB created?
We create KDP-ready EPUB files from your manuscript — from £69 with unlimited revisions.
Format my book →You might also need
- EPUB Validation Errors
- KDP File Formats
- KDP Formatting Checklist
- Word to KDP Guide
- Free Open-Source Tools for Self-Publishers
Further reading from official sources
- KDP — Supported eBook formats — Amazon's official supported-format list.
- W3C — EPUB 3.3 specification — the underlying EPUB standard.
Related Tools
Quick verdict
Use this if:
- You're publishing your first 1-3 books and want a fast workflow
- You don't want to learn complex software
- Cross-platform compatibility matters
Skip it if:
- You're publishing 10+ books and need granular control
- Your books have complex layouts (cookbooks, picture books)
- You already have a workflow that works
Best alternative: depends on your priority — speed (paid tool), price (free Calibre), or polish (paid service).
