MOBI vs PDB
A detailed comparison of Mobipocket eBook and PalmDOC eBook — file size, quality, compatibility, and which format to choose for your workflow.
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Ghostscript + QPDFChoosing between MOBI (Mobipocket eBook, application/x-mobipocket-ebook) and PDB (PalmDOC eBook, application/x-palm-database) depends on your target workflow, compression efficiency, and device support. Below is our side-by-side technical benchmark and instant bidirectional converter.
MOBI vs PDB at a glance
MOBI vs PDB| Dimension | .MOBI | .PDB |
|---|---|---|
| Format Name | Mobipocket eBook (.mobi) | PalmDOC eBook (.pdb) |
| Format Family | eBooks | eBooks |
| Primary MIME | application/x-mobipocket-ebook | application/x-palm-database |
| Developer / Year | Mobipocket SA (2000) | Palm Inc. (1996) |
| Pipeline Role | Read & Write | Read & Write |
When should you use MOBI vs PDB?
.MOBI Use when…
Use MOBI (Mobipocket eBook) when your pipeline requires native application/x-mobipocket-ebook compatibility, predictable rendering, or specialized eBooks editing support.
.PDB Use when…
Use PDB (PalmDOC eBook) when you need application/x-palm-database delivery, cross-platform eBooks distribution, or streamlined storage.
Technical Specifications
| Specification | .MOBI | .PDB |
|---|---|---|
| MIME type | application/x-mobipocket-ebook | — |
| Extension | .mobi, .prc (PalmDOC variant) | .pdb |
| Container | Palm Database (PDB) | — |
| Markup | Compressed HTML subset | — |
| Successor | .azw, .azw3 (Kindle-specific) | — |
| MIME types | — | application/vnd.palm (Palm), chemical/x-pdb (biochemistry) |
| Palm structure | — | Header + record list + record data |
| Related formats | — | PalmDOC, Mobipocket MOBI, AZW |
| Namespace clash | — | Biochemistry Protein Data Bank is a different format entirely |
Strengths Comparison
.MOBI Strengths
- Universal Kindle support on every device ever released.
- Very small file sizes for text-heavy books.
- Mature tooling via Calibre and Amazon's KindleGen.
- Simple container structure — easy to parse.
.PDB Strengths
- Compact record-based structure for low-RAM devices.
- Basis of PalmDOC, Mobipocket, eReader, and Kindle AZW formats.
- Well-documented.
- Simple to parse — stable for 30 years.
Limitations
.MOBI — Limitations
- Deprecated by Amazon for new uploads since 2022.
- Poor support for rich typography (drop caps, ligatures, fixed layout).
- No embedded fonts in the base format.
- Proprietary container discouraged use outside Kindle.
- Effectively a legacy format — new books go to AZW3/EPUB.
.PDB — Limitations
- Ecosystem collapsed with Palm's hardware business.
- Name collides with biochemistry's Protein Data Bank PDB.
- Modern ebook tooling prefers EPUB, AZW3, or direct formats.
- Very little new content written as PDB in 2026.
Technical deep dive: MOBI vs PDB
Both MOBI and PDB serve distinct roles in modern digital pipelines. With KaijuConverter you can transcode between .mobi and .pdb in seconds while preserving metadata and structural fidelity.
Frequently Asked Questions
MOBI (Mobipocket eBook) uses MIME type application/x-mobipocket-ebook in the eBooks family, whereas PDB (PalmDOC eBook) uses application/x-palm-database in the eBooks family. Each optimizes for different trade-offs in file size, fidelity, and software compatibility.
Yes. KaijuConverter uses tuned encoding profiles to preserve maximum visual, audio, or document fidelity when converting between MOBI and PDB.
MOBI (Mobipocket eBook) is an ebook format designed for reading long-form text on dedicated e-readers, tablets, and ebook apps. It is part of the ebooks family and typically supports reflowable text, embedded images, chapter navigation, cover art, and metadata (title, author, ISBN) in a portable package.
PDB (PalmDOC eBook) is an ebook format designed for reading long-form text on dedicated e-readers, tablets, and ebook apps. It is part of the ebooks family and typically supports reflowable text, embedded images, chapter navigation, cover art, and metadata (title, author, ISBN) in a portable package.
Dedicated e-readers — Kindle, Kobo, Nook, Pocketbook — support the most common ebook formats. On phones, Apple Books, Google Play Books, Moon+ Reader and KOReader all handle MOBI. For desktop reading, Calibre is the universal ebook viewer and library manager. Convert to EPUB or PDF for maximum compatibility.
Dedicated e-readers — Kindle, Kobo, Nook, Pocketbook — support the most common ebook formats. On phones, Apple Books, Google Play Books, Moon+ Reader and KOReader all handle PDB. For desktop reading, Calibre is the universal ebook viewer and library manager. Convert to EPUB or PDF for maximum compatibility.
Upload your MOBI to KaijuConverter and pick EPUB, MOBI, PDF, AZW3, or similar targets. Our Calibre-powered pipeline preserves chapter structure, embedded images, cover art, and metadata. Conversion takes seconds for typical novels; long technical books with many images may take a little longer.
EPUB is the open ebook standard — it plays on every e-reader except older Kindles and in every major ebook app. PDF is better for fixed-layout content (textbooks, coffee-table books) and printing. Pick EPUB when the ebook is reflowable text, PDF when the layout matters more than the reading experience.
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