CONVERT
PDB → MOBI
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Fast, secure PDB to MOBI conversion. No registration required.
PDB is an ebook-family format used for digital reading on e-readers and reading apps. Reaching a MOBI from there is one hop. Going from PDB to MOBI preserves the book structure — ToC, chapters, cover image, bold/italic runs, embedded fonts where licensing permits — and emits a MOBI file that reflows correctly on small screens. The pipeline handles the CSS remapping and image re-encoding automatically. Context: PDB is an ebook-family format used for digital reading on e-readers and reading apps. MOBI is Amazon's legacy Mobipocket ebook format, the older Kindle delivery format.
PalmDOC eBook
Source formatPDB (Palm Database) is a generic database format from the Palm OS era that was widely used for ebooks on Palm handheld devices. PalmDOC and Mobipocket both use PDB as their underlying container for storing text-based ebook content.
Mobipocket eBook
Target formatMOBI is the Mobipocket eBook format historically used by Amazon Kindle devices. While Amazon has moved to newer formats, MOBI remains relevant for older Kindles and legacy eBook libraries.
Why convert PDB to MOBI
Library applications (Calibre, Apple Books, Kindle library) prefer a single format for indexing. Converting mixed PDB/MOBI collections to one canonical MOBI makes search, filter and sync work reliably.
HOW TO CONVERT
PDB → MOBI
Start the job
Upload a PDB; we read metadata, cover image and table of contents from the source container.
Rewrite as MOBI
The content is flowed into the MOBI format with appropriate CSS, images re-encoded at recommended dimensions.
Save the ebook
Download the MOBI. Side-load to your device or drop into your reader library.
Common Use Cases
Share across platforms
Send MOBI files to anyone without worrying about whether they have the right software for PDB.
Embed in documents
Drop MOBI output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
MOBI often produces smaller files than PDB for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
PDB vs MOBI — Strengths and limitations
What each format does best, and where it falls short.
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
- 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.
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.
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.
PDB vs MOBI — Technical specifications
Side-by-side comparison of the technical details.
PDB
- MIME types
- application/vnd.palm (Palm), chemical/x-pdb (biochemistry)
- Extension
- .pdb
- Palm structure
- Header + record list + record data
- Related formats
- PalmDOC, Mobipocket MOBI, AZW
- Namespace clash
- Biochemistry Protein Data Bank is a different format entirely
MOBI
- Extension
- .mobi, .prc (PalmDOC variant)
- MIME type
- application/x-mobipocket-ebook
- Container
- Palm Database (PDB)
- Markup
- Compressed HTML subset
- Successor
- .azw, .azw3 (Kindle-specific)
| Specification | PDB | MOBI |
|---|---|---|
| MIME types | application/vnd.palm (Palm), chemical/x-pdb (biochemistry) | — |
| Extension | .pdb | .mobi, .prc (PalmDOC variant) |
| Palm structure | Header + record list + record data | — |
| Related formats | PalmDOC, Mobipocket MOBI, AZW | — |
| Namespace clash | Biochemistry Protein Data Bank is a different format entirely | — |
| MIME type | — | application/x-mobipocket-ebook |
| Container | — | Palm Database (PDB) |
| Markup | — | Compressed HTML subset |
| Successor | — | .azw, .azw3 (Kindle-specific) |
PDB vs MOBI — Typical file sizes
Approximate file sizes for common scenarios.
PDB
- PalmDOC ebook (text novel) 200 KB - 2 MB
- PalmOS app data store 10 KB - 500 KB
- Protein Data Bank file (biochemistry) 50 KB - 5 MB
MOBI
- Text-only novel 200 KB - 1 MB
- Illustrated book 2-10 MB
Quality & Compatibility
DRM-protected PDB files cannot be converted — KaijuConverter respects publisher encryption and returns an error rather than stripping protection. Unprotected or self-published PDB ebooks convert without restriction.
Tips for Best Results
- Use structure detection (TOC > chapters) to regenerate a clean table of contents in the MOBI if the PDB has none.
- Embedded fonts bloat file size — consider dropping them in Advanced if your reader uses its own typography anyway.
- For serialised fiction, keep cover art consistent across episodes by re-using one MOBI cover rather than auto-generating per PDB.
Frequently Asked Questions
Yes. The free tier accepts files up to 25 MB without registration, email capture or watermarks; paid plans go up to 2 GB. Paid plans raise the size cap, enable batch conversions and provide a REST API for automation, but nothing on the free tier is quality-limited — the output is exactly the same as on any paid plan.
Yes, provided the PDB itself has a well-formed ToC. Calibre reads the navigation structure and writes an equivalent ToC into the MOBI. If the source lacks a ToC we can generate one from heading levels in Advanced → structure detection.
Uploads run over HTTPS, files are processed in isolated containers, and both the source PDB and the MOBI output are auto-deleted within two hours. No account is required, file contents are never logged, and KaijuConverter does not use uploads for AI training. The paid plan adds a signable data-processing agreement for regulated workflows.
No. KaijuConverter does not strip digital rights management. DRM-free PDB files — anything you authored yourself, public-domain classics, files from DRM-free retailers — convert without any restriction.
Most files finish in well under a minute. Small images and documents are typically ready in a few seconds; large video or audio files scale roughly with duration. Upload speed from your network is usually the dominant factor, not server time.
Yes. The cover is extracted from the PDB and re-embedded in the MOBI at device-appropriate dimensions. You can also override it in Advanced by uploading a custom cover image alongside the book file.
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Read guideSecure & Private Conversion
Your files are encrypted during transfer, processed in isolated containers, and automatically deleted within 60 minutes. We never read, share, or store your data.