What is PRC? Palm/Mobipocket Ebook Format Explained

What is PRC?

PRC (Palm Resource/Database file) is a container format originating from the Palm OS platform that has been widely used to store ebooks. In the ebook context, PRC files most commonly hold Mobipocket or PalmDOC content for reading on handheld devices.

Technically, a PRC ebook is a Palm Database (PDB) file containing compressed text and, for Mobipocket, the same XHTML-based content found in MOBI files. Because Mobipocket and MOBI share this container, .prc and .mobi files are closely related, and the format was carried into early Kindle and Mobipocket Reader workflows.

How PRC Works

The .prc extension is a little confusing because it names a container structure rather than one specific book format. At its root, PRC stands for Palm Resource, and it uses the Palm Database (PDB) file structure that originated on Palm handheld devices. That structure is essentially a simple container: a header followed by a series of numbered records, which the software reading it interprets according to the type of content stored inside.

In the ebook world, a .prc file almost always holds a Mobipocket book. Mobipocket built its ebook format on top of the Palm database container, so a Mobipocket .prc stores the book's content, marked up in a simplified HTML, as a sequence of records inside that PDB wrapper. The reading software walks the records to reassemble the chapters, images, and table of contents into a readable book.

The text content is typically compressed with a lightweight scheme such as PalmDOC compression, which was designed to be easy to decompress on the very limited hardware of early handhelds. Images and other resources are stored as their own records within the same file. This record-based design kept memory use low, which mattered enormously on the devices PRC was born on.

Functionally, a Mobipocket .prc file offers reflowable text that adapts to the screen, basic formatting, embedded images, bookmarks, and a navigable table of contents. It supports the core reading experience well, but its simplified markup means it cannot express the rich typography and layout that later standards introduced.

History and Standardization

The PRC container traces back to the Palm OS era of handheld organizers, where the Palm database format was the standard way to store both applications and data. The Mobipocket company adopted this container for its ebook software, and .prc became one of the common extensions for Mobipocket books, alongside .mobi.

Mobipocket's history connects directly to the modern ebook world because Amazon acquired Mobipocket in the mid-2000s and built its early Kindle formats on that technology. This is why old Mobipocket and PRC files are so closely related to the original Kindle formats: they share a lineage. The result is that a Mobipocket .prc can often be opened by Kindle software and by many third-party readers.

Today PRC is best described as a legacy format. Palm devices are long gone, Mobipocket's software is discontinued, and Amazon moved on to newer Kindle formats like KF8. Files with a .prc extension still exist in older collections and remain readable in various apps, but no one is creating new books in it, and it has been superseded for all practical purposes.

PRC Compared to MOBI, EPUB, and Kindle Formats

Against MOBI, there is often no meaningful difference at all: .prc and .mobi frequently hold the same Mobipocket content, and the extension is largely a matter of convention. Both are legacy Mobipocket formats with the same simplified markup and the same limitations, so the choice between them is usually cosmetic rather than technical.

Against EPUB and the newer Kindle format AZW3, PRC is clearly the older and weaker relative. Those formats are built on modern HTML and CSS and support embedded fonts, precise styling, and complex layouts, while PRC's simplified markup produces plain, reflowed text with only basic formatting. For any book where design matters, the newer formats are far better.

In practice, PRC matters mainly for compatibility with old files and old devices. If you have a legacy Mobipocket library, PRC is what you already own, and most readers can still open it. For anything new, however, the sensible path is to convert PRC to EPUB or a current Kindle format, which is straightforward given how closely these formats are related, and which gains you modern features and broad support.

MKV Technical Specifications

PRC vs Other Ebook Formats

PRC is essentially a Mobipocket file in a Palm container, so it shares MOBI's behavior, whereas EPUB is the open, broadly supported alternative.

Advantages & Disadvantages

Common Use Cases

PRC is encountered mainly as a legacy handheld ebook format.