MOBI (Mobipocket eBook Format)
MOBI is an e-book format originally developed by Mobipocket and later adopted by Amazon for early Kindle devices. It supports reflowable text, bookmarks, annotations, and DRM. MOBI has been largely superseded by Amazon's KF8 (AZW3) format but remains common for legacy Kindle files.
MIME Type
application/x-mobipocket-ebook
Type
Binary
Compression
Lossless
Advantages
- + Compatible with all Kindle devices and the Kindle app
- + Supports bookmarks, highlights, and annotations
- + Small file sizes for text-heavy books
Disadvantages
- − Proprietary format controlled by Amazon
- − Limited formatting compared to EPUB 3
- − Being phased out in favor of KF8/AZW3 for newer Kindles
When to Use .MOBI
Use MOBI only for compatibility with older Kindle devices; for modern e-book distribution prefer EPUB or KF8 (AZW3).
Technical Details
MOBI files use a PalmDOC database structure with PDB headers, HTML content, and optional MOBI-specific metadata records. DRM is applied through Amazon's proprietary encryption layer.
History
Mobipocket SA created the MOBI format in 2000 for Palm OS devices. Amazon acquired Mobipocket in 2005 and used MOBI as the basis for the original Kindle file format before transitioning to KF8.