CONVERT
FB2 → PDB
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Fast, secure FB2 to PDB conversion. No registration required.
Why this pair exists — FB2 is FictionBook, a popular XML-based open ebook format in Russian-speaking markets. Ergo, the PDB route. A PDB converted from a FB2 is a new ebook container with the same content inside. The text body survives losslessly; formatting survives as closely as the PDB container supports it; cover images are re-embedded at the target's recommended dimensions. A quick refresher — FB2 is FictionBook, a popular XML-based open ebook format in Russian-speaking markets. By contrast, PDB is an ebook format tuned for reflowable reading on e-readers and mobile devices.
FictionBook
Source formatFictionBook (FB2) is an XML-based eBook format popular in Russia and Eastern Europe. It provides structured semantic markup for fiction and non-fiction books.
PalmDOC eBook
Target 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.
Why convert FB2 to PDB
Library applications (Calibre, Apple Books, Kindle library) prefer a single format for indexing. Converting mixed FB2/PDB collections to one canonical PDB makes search, filter and sync work reliably.
HOW TO CONVERT
FB2 → PDB
Start the job
Upload a FB2; we read metadata, cover image and table of contents from the source container.
Rewrite as PDB
The content is flowed into the PDB format with appropriate CSS, images re-encoded at recommended dimensions.
Save the ebook
Download the PDB. Side-load to your device or drop into your reader library.
Common Use Cases
Language-learning ebooks
Dictionary lookup and sentence highlighting work better on PDB in most reader apps than on FB2.
Technical book reading
Code blocks and tables render more reliably in PDB across devices; FB2 can break them on narrow screens.
Audiobook companion
Whispersync-style features expect PDB; convert the FB2 of your book to pair text and audio.
Giveaways and mailing lists
Subscribers want a PDB they can open instantly; a FB2 introduces install friction that kills open rates.
FB2 vs PDB — Strengths and limitations
What each format does best, and where it falls short.
FB2 Strengths
- Pure XML — trivial to parse, search, and transform.
- Single-file ebooks with inline images.
- Excellent on low-powered e-readers.
- De-facto standard in Russian-language ebook ecosystem.
- Simple structure makes conversion to any other format straightforward.
Limitations
- No styling, no custom fonts, no fixed layouts.
- Minimal Western-language tooling.
- Kindle and Apple Books do not support FB2 natively.
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.
FB2 vs PDB — Technical specifications
Side-by-side comparison of the technical details.
FB2
- MIME type
- application/x-fictionbook+xml
- Extensions
- .fb2, .fb2.zip
- Container
- Single XML file (optionally zipped)
- Standard
- FictionBook community spec (maintained on GitHub)
- Encoding
- UTF-8 (required)
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
| Specification | FB2 | PDB |
|---|---|---|
| MIME type | application/x-fictionbook+xml | — |
| Extensions | .fb2, .fb2.zip | — |
| Container | Single XML file (optionally zipped) | — |
| Standard | FictionBook community spec (maintained on GitHub) | — |
| Encoding | UTF-8 (required) | — |
| 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 |
FB2 vs PDB — Typical file sizes
Approximate file sizes for common scenarios.
FB2
- Novel (text only) 200-800 KB
- Novel with cover image 300 KB - 1.5 MB
- Illustrated children's book 5-30 MB
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
Quality & Compatibility
DRM-protected FB2 files cannot be converted — KaijuConverter respects publisher encryption and returns an error rather than stripping protection. Unprotected or self-published FB2 ebooks convert without restriction.
Tips for Best Results
- Use structure detection (TOC > chapters) to regenerate a clean table of contents in the PDB if the FB2 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 PDB cover rather than auto-generating per FB2.
Frequently Asked Questions
Yes. The free tier accepts files up to 100 MB without registration, email capture or watermarks. 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 FB2 itself has a well-formed ToC. Calibre reads the navigation structure and writes an equivalent ToC into the PDB. 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 FB2 and the PDB 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 FB2 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 FB2 and re-embedded in the PDB 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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