What is the PDG file format?
The .pdg file is a proprietary page-image ebook format developed by Beijing SuperStar Electronic Technology Co., Ltd. (北京超星电子技术有限公司) for its SuperStar digital library platform. It is primarily found in Chinese academic and public library systems, where SuperStar (超星) has digitized over 500,000 titles. The format stores scanned book pages as compressed images rather than reflowable text, making it conceptually similar to DjVu documents.
Each .pdg file begins with a 140-byte binary header. The first three bytes are 0x48 0x48 0x02 (ASCII HH followed by 0x02), and the byte at offset 3 identifies the compression method: 0x00 for CCITT Group 4 (black-and-white fax compression), 0x01 for JPEG, 0x02 for DjVu, or 0x03 for PNG. Because pages are stored as images, .pdg files cannot be reflowed or searched as text without OCR processing.
The official reader is SSReader (超星阅读器), also distributed as the Chaoxing app on Android and iOS. Institutional library copies may carry DRM encryption. Western users rarely encounter .pdg files; within China, the format competes with CAJ (used by CNKI) and PDF. PDG is declining as PDF becomes the dominant standard for Chinese digital library content.
Security & safety
RISK: LOWStatic page-image document. No executable code, macros, or scripts. DRM mechanism is proprietary but does not pose a security risk to the device.
Format details
in a nutshellPrograms that open PDG files
Windows1 app
SSReader (超星阅读器 / Chaoxing Reader)
Free Download and install SSReader from chaoxing.com; double-click the PDG file or use File → Open. DRM-protected files require library login. 
Android1 app
Chaoxing (超星) mobile app
Free Install the Chaoxing app; sign in with your library account to access and read PDG ebooks.
Chaoxing (超星) mobile app
Free Install the Chaoxing app from App Store; sign in with library account. Technical details
deep spec| File encoding | Binary, little-endian |
| Magic bytes | `0x48 0x48 0x02` (ASCII `HH` + `0x02`) at offset 0 |
| Header size | Fixed 140 bytes |
| Compression flag | Byte at offset 3: `0x00` = CCITT Group 4, `0x01` = JPEG, `0x02` = DjVu, `0x03` = PNG |
| Content model | Scanned page images - not reflowable text; OCR required to extract searchable text |
| Color depth | 1 bpp (CCITT Group 4 black-and-white) to 24 bpp (JPEG/PNG color pages) |
| DRM | Encryption possible in institutional/library copies; personal copies may be unencrypted |
| Typical file size | 100 KB - 50 MB (varies by page count and compression method) |
| MIME type | application/octet-stream (no IANA-registered MIME) |
| Official reader | SSReader (超星阅读器) / Chaoxing app (Windows, Android, iOS) |
| Platform support | Windows, Android, iOS |
| Developer | Beijing SuperStar Electronic Technology Co., Ltd. (北京超星电子技术有限公司) |
| Scale of use | 500,000+ digitized titles in Chinese academic and public libraries; primarily encountered in China |
| Competing formats | CAJ (CNKI platform) and PDF are both increasingly dominant in Chinese digital library publishing |
| Released | late 1990s |
| Latest version | PDG v2 (extended header with DjVu/PNG compression support) |
PDG conversions
Community Q&A
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