What is a PDB file?

PDB is a binary format, meaningful only to a program that knows it. It is used for handing a finished file over.

The extension is .pdb, and the full name is Palm Database E-book. Both matter less than what the file can hold, which is what the rest of this page is about.

Palm published it in 1996.

A format that has been readable for that long is a format worth trusting with something you want back in ten years.

It is written down and implementable, though the vendor decides what the next version looks like. In practice that is enough for the file to keep opening; it is not enough to be sure of it.

The people who made it have moved on, and support is being withdrawn rather than added. Anything still in this format is worth moving while the tools to move it are still around.

PDB is not limited to one page, which matters when converting to something that is: one conversion produces one file holding a single page — the first one, unless the page is something the converter lets you pick.

Calibre reads it, and so do most programs of the same kind.

If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.

No browser reads it.

That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.

PDB is meant to be handed over rather than worked in. Editing one is possible and rarely pleasant; the sane approach is to change the source and export again.

The recurring complaints: support outside its home ground is uneven.

None of these is a reason to avoid the format. They are the things worth knowing before you are surprised by one, which is a different claim and a more useful one.

This page is about the Palm database — the container used by PalmOS handhelds and, most often, by the e-book readers that ran on them. If that is not what you have, two other things use the same extension and are entirely unrelated.

A Protein Data Bank file is a text format describing the three-dimensional structure of a molecule, used in structural biology; open it in a text editor and you will see columns of atom coordinates. A program database is a Visual Studio debug file that maps compiled code back to source; it sits beside an executable and is binary. Neither has anything to do with the other, or with this page.

The Palm database is a wrapper: a header, a list of records, and inside them whatever the application put there. What the file actually contains is identified by a four-character creator and type code in that header — so two PDB files can be completely different things.

That is why "how do I open a PDB file" has no single answer. An address book, a memo store, a game save and an e-book are all valid PDB files, and the only way to know which you have is to look at the type code or the file’s origin.

The PDB files that survive are overwhelmingly books. PalmOS was the first genuinely usable e-reading platform, and several reader applications stored their books this way — eReader, which is the commonest, plus Mobipocket, which used PDB as its container before Amazon bought the company and turned it into MOBI.

That last point is the useful one. A Mobipocket PDB is a MOBI in a Palm wrapper, so tools that read MOBI often read it directly, and the conversion path is the same. An eReader PDB is a different thing again and needs a tool that specifically understands it.

Calibre is the practical answer and reads several of the e-book variants, converting to EPUB. That is the right destination: an open standard, read by every current e-reader, and the format anything else can be generated from later.

What tends to be lost is formatting rather than text. These books were made for a 160 by 160 pixel greyscale screen — the styling was minimal to begin with, and what exists is often bespoke to one reader application. The text and the chapter structure come across; anything more elaborate probably was not there.

eReader books bought from a store were protected, and the scheme was unusual: the key was derived from the purchaser’s name and credit card number. That was a deliberately friendly design at the time — no activation server, no account, nothing to go offline.

It aged better than most DRM for exactly that reason, but the practical position now is that a protected file needs details from a purchase made fifteen or twenty years ago. If you have them, tools exist; if not, the book is not recoverable, and this site does not do that work either way.

If the handheld still runs, its synchronisation software wrote the PDB files to a folder on the desktop computer it was paired with — usually under a user name inside the Palm directory. That is where an archive of memos, addresses and books will be, and copying the folder is the whole backup.

For non-book data, converting is less about format and more about extraction: memos and addresses were plain enough that free tools can dump them to text or CSV. It is worth doing while the tools still exist, which is the same advice as for every other format on this page and for the same reason.

Almost entirely for archival reasons. Nothing writes Palm databases, no current device reads them, and the platform ended in 2010. A file that turns up now came off an old machine, a backup drive or an inherited computer.

The lesson it illustrates is a familiar one on this site: a container whose meaning depends on a four-character code registered with a company that no longer exists is a container whose contents become guesswork. Convert to something open while a tool that understands it is still maintained.