Free Online EPUB to MOBI Converter
Convert EPUB to MOBI online for free.
| File name | Size | Convert to |
|---|
Pick a format to convert to.
Checking files and selected output formats.
What to expect when converting EPUB to MOBI
A 500 KB EPUB typically becomes 550 – 600 KB as MOBI.
Quality: Text and chapter structure preserved. Some CSS styling and advanced layout from EPUB 3 may not render in MOBI.
Best for: reading on older Kindle devices that don't support EPUB natively.
Avoid when: you have a modern Kindle (post-2022) which supports EPUB directly via "Send to Kindle".
Tip: Amazon now accepts EPUB via "Send to Kindle", MOBI is mostly obsolete unless you have a pre-2022 Kindle.
EPUB to MOBI - A modern ebook for side-loading to an older Kindle
MOBI is for older Kindles, roughly pre-2018 Paperwhite and Oasis hardware. Anything newer takes an EPUB directly through Send to Kindle, so the conversion is only worth running when you are side-loading over USB to an older device, or when a self-publishing tool asks for MOBI by name. For anything starting today, EPUB or the newer AZW3 are the better targets.
EPUB to MOBI: converting for older Kindle devices
MOBI (Mobipocket) is Amazon's older ebook format used by legacy Kindle devices. Both EPUB and MOBI contain reflowable HTML content, but MOBI uses a different packaging structure and supports a subset of CSS compared to EPUB. The conversion repackages the HTML content, converts or simplifies CSS styles, regenerates the table of contents in MOBI's format, and applies PalmDOC or HUFF/CDIC compression. Modern Kindle devices support KFX and EPUB, making MOBI increasingly obsolete.
Convert EPUB to MOBI for sideloading onto older Kindle devices (pre-2022 models) that don't support EPUB natively. Newer Kindle devices accept EPUB directly via USB or Send-to-Kindle. Amazon also recommends uploading EPUB for Kindle publishing rather than MOBI.
EPUB vs MOBI: Side-by-side
Technical comparison of the two formats, useful for deciding which to use, or for confirming what changes during conversion.
| Property | EPUB | MOBI |
|---|---|---|
| Full name | Electronic Publication | Mobipocket eBook |
| Year introduced | 2007 | 2000 |
| Developer / standard body | W3C (formerly IDPF) | Mobipocket / Amazon |
| MIME type | application/epub+zip | application/x-mobipocket-ebook |
| File extension | .epub | .mobi |
| Compression | ZIP-compressed XHTML + CSS | PalmDOC compression |
| Color / data depth | N/A | N/A |
| Max dimensions / size | Software-limited | Software-limited |
| Transparency | No | No |
| Animation | No | No |
| Standard / specification | W3C EPUB 3.3 / ISO/IEC 23736 | Mobipocket |
| Best for | Apple Books, Kobo, Nook, Google Play Books, reflowable text | Older Kindle devices (replaced by AZW3 then KFX) |
Use EPUB when
- You want a format that works on every non-Kindle e-reader
- You're publishing an ebook and picking one format
- You're archiving a library for long-term readability
- You're sending books to friends who don't use Kindle
Use MOBI when
- You're dealing with pre-2018 Kindle purchases
- You have a legacy MOBI library you're maintaining
- A specific legacy Kindle device requires it
In 2026, EPUB is the answer for almost everyone. Amazon's Send-to-Kindle now accepts EPUB directly, so even Kindle owners don't strictly need MOBI or AZW3 anymore. Convert MOBI collections to EPUB for a future-proof library, the reverse conversion (EPUB to MOBI) only makes sense for specific legacy Kindle workflows.