Quick Verdict
Use EPUB when…
Use EPUB for publishing to Apple Books, Kobo, Nook, Google Play Books, Smashwords, and any platform that isn't Amazon. EPUB is the ISO standard for digital publishing.
Use AZW3 when…
Use AZW3 for Kindle devices and Kindle apps. Books purchased from Amazon Kindle Store are AZW3. For self-publishing to Amazon KDP, upload EPUB and Amazon converts it automatically.
EPUB vs AZW3: Feature Comparison
| Feature | EPUB | AZW3 |
|---|---|---|
| Supported by | All e-readers except Kindle | Kindle devices and Kindle apps only |
| Open standard | Yes (IDPF/W3C) | No (Amazon proprietary) |
| CSS support | CSS2 + limited CSS3 | Better CSS3 support than MOBI |
| JavaScript | EPUB3 supports limited JS | Limited |
| DRM | Adobe DRM, Apple DRM | Amazon DRM (KFX layer) |
| Self-publishing | Upload directly to non-Amazon stores | Amazon KDP converts from EPUB automatically |
| Conversion | Calibre can convert to/from AZW3 | Calibre can convert to EPUB (DRM-free only) |
When EPUB wins
- ✓Supported by: All e-readers except Kindle
- ✓Open standard: Yes (IDPF/W3C)
- ✓CSS support: CSS2 + limited CSS3
When AZW3 wins
- ✓Supported by: Kindle devices and Kindle apps only
- ✓Open standard: No (Amazon proprietary)
- ✓CSS support: Better CSS3 support than MOBI
Frequently asked questions
Can Kindle read EPUB files?
Newer Kindles (Paperwhite 11th gen 2021+, Kindle Scribe, all Kindle apps) support EPUB natively via Send to Kindle. Older Kindles require MOBI or AZW3. Amazon's 'Send to Kindle' service accepts EPUB and converts automatically. For self-publishing: Amazon KDP accepts EPUB directly and converts to AZW3 for delivery to customers.
How do I convert AZW3 to EPUB?
DRM-free AZW3: Calibre converts AZW3 to EPUB — add the file to Calibre, right-click → Convert Books → Output Format: EPUB. DRM-protected AZW3 (Amazon purchases): requires DRM removal first (DeDRM plugin for Calibre, which is legal in some jurisdictions for personal use). Always check local laws. Amazon purchases are licensed content — check terms before converting.
Is AZW3 better than MOBI?
Yes. AZW3 (KF8) supports proper CSS, HTML5 elements, embedded fonts, and SVG — all lacking in the older MOBI format. MOBI limited formatting to basic HTML4-era styling. Amazon deprecated MOBI delivery for new Kindle books in 2022. If you have MOBI files, convert to AZW3 or EPUB using Calibre for better formatting compatibility on modern Kindles.
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