About PDB Files

PalmDOC eBook

Released 1996 By Palm Inc.

PDB (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.

Family

eBooks

Extension

.pdb

MIME Type

application/x-palm-database

Can Use As

Input Output

The story

HOW PDB
CAME TO BE.

1996

2007

2010

The .pdb extension — in this context, Palm Database — dates from the PalmPilot handhelds that Palm Inc. shipped in 1996. The operating system used a simple record-oriented filesystem: each application’s data and every document (ebooks, to-do lists, memos) was a PDB file, holding a sequence of numbered records. PalmDOC, Mobipocket, eReader, and iSilo all used variations of the PDB container to ship ebooks to PalmOS devices.

When Palm’s hardware business collapsed around 2010, PDB faded alongside it — but not before Amazon’s first Kindle (2007) inherited the PDB container structure as the basis of its AZW format. Every Kindle book since 2007 is structurally a PalmDOC-style PDB under the hood. The extension also collides with "Protein Data Bank" PDB files used in biochemistry (plain text coordinate data for molecules) — context determines which one a file actually is.

CURIOSITIES &
TRIVIA.

Palm Database structure lives on inside every Kindle ebook — Amazon's AZW format is built on the PalmDOC PDB container from 1996.

.pdb ambiguity: in biochemistry, "PDB" means Protein Data Bank, a plain-text format for molecular coordinates — the biochemist's PDB looks nothing like Palm's.

The original PalmPilot shipped with 128 KB of RAM — PDB's record-based structure was designed to fit in that footprint.

Mobipocket's MOBI format (which Amazon bought in 2005) was a PalmDOC PDB derivative — part of why Kindle AZW inherited PDB mechanics.

Palm Inc. was acquired by HP in 2010 for $1.2 billion, then effectively wound down — ending the primary PDB ecosystem.

STRENGTHS &
LIMITATIONS.

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.
Very little new content written as PDB in 2026.

Typical Sizes & Weights

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

Technical Specifications

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

CONVERT FROM
PDB

pdb pdf pdb docx pdb odt pdb txt pdb md pdb html pdb epub pdb mobi pdb azw3 pdb fb2 pdb rst pdb htmlz pdb txtz pdb lrf pdb snb

CONVERT TO
PDB

epub pdb mobi pdb azw3 pdb fb2 pdb htmlz pdb txtz pdb lrf pdb snb pdb lit pdb cbz pdb cbr pdb

Common Use Cases

Legacy Palm OS ebooks, PalmDOC content, vintage handheld reading