Convert AZW3 to MOBI online for free.
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MOBI is Amazon's older Kindle format, now largely superseded by AZW3 and KFX. Convert to MOBI when you need side-load compatibility with older Kindle devices (pre-2015 Paperwhite and earlier) or when a self-publishing service specifies MOBI. For modern Kindles, upload EPUB directly to Amazon KDP and let Amazon transcode.
Technical comparison of the two formats — useful for deciding which to use, or for confirming what changes during conversion.
| Property | AZW3 | MOBI |
|---|---|---|
| Full name | Kindle Format 8 | Mobipocket eBook |
| Year introduced | 2011 | 2000 |
| Developer / standard body | Amazon | Mobipocket / Amazon |
| MIME type | application/vnd.amazon.ebook | application/x-mobipocket-ebook |
| File extension | .azw3 | .mobi |
| Compression | Variable | PalmDOC compression |
| Color / data depth | N/A | N/A |
| Max dimensions / size | Software-limited | Software-limited |
| Transparency | No | No |
| Animation | No | No |
| Standard / specification | Amazon | Mobipocket |
| Best for | Modern Kindle devices — enhanced typography and layout | Older Kindle devices (replaced by AZW3 then KFX) |
AZW3, also known as Kindle Format 8 (KF8), is Amazon's modern ebook format introduced in 2011 as the successor to MOBI. Built on HTML5 and CSS3, AZW3 supports advanced typographic features including embedded fonts, drop caps, SVG graphics, fixed-layout pages, and responsive design that adapts to different Kindle screen sizes. It provides a significantly richer reading experience compared to the older MOBI format.
AZW3 is Amazon's proprietary format and only works on Kindle devices and Kindle reading apps. It takes full advantage of Kindle's enhanced typesetting engine, supporting features like X-Ray, Word Wise, and improved font rendering. AZW3 files use more efficient compression than MOBI, resulting in smaller file sizes. While AZW3 is the preferred format for sideloading content to modern Kindles, it cannot be read on other eReaders like Kobo, Nook, or Apple Books without first converting to EPUB.
Quick answers about compatibility, quality, metadata handling, and the most common reasons to convert AZW3 files to MOBI.
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