What is the PCX file format?
The .pcx format - short for PiCture eXchange - is one of the oldest raster image file extensions in PC history, introduced in 1985 by ZSoft Corporation with *PC Paintbrush* for MS-DOS, years before Windows became widespread. While it has since been outdated and replaced by more capable formats such as PNG and BMP, it was developed as a binary raster image format using simple lossless run-length encoding (RLE) compression.
A .pcx file begins with a fixed 128-byte header that identifies the version, color depth, image dimensions, and dots-per-inch resolution. The format supports several color depths: 1-bit black-and-white, 4-bit (16-color), 8-bit indexed (256-color), and 24-bit truecolor stored across three 8-bit color planes. Version 5 of the specification - the most widely supported today - added 256-color VGA palette support and full 24-bit output; the 256-color palette is appended at the very end of the file as a 769-byte block rather than embedded in the header.
It is still supported by a variety of image processing applications from Adobe, Corel, and others. Multi-page .pcx images can be bundled into the related .dcx container format, commonly used for fax documents.
Security & safety
RISK: LOWPCX is a passive, well-understood raster format with no scripting or macros, so opening one is low-risk. The only real-world cautions are non-malware: PCX RLE decoders in very old or poorly written software have historically had buffer-overflow bugs on malformed files, so use a current, maintained viewer (IrfanView, XnView, GIMP, ImageMagick) from its official site rather than a random 'PCX viewer' download that may bundle adware. Convert anything you need to keep to PNG for long-term safety and compatibility.
Format details
in a nutshellPrograms that open PCX files
Windows5 apps
IrfanView
Free File > Open the .pcx to view; Save As to export PNG/JPG/BMP. Batch-converts whole folders. 
macOS3 apps
Linux3 apps
ImageMagick
Open-source Command line: 'convert image.pcx image.png' to view-convert; reads/writes PCX natively. Technical details
deep spec| Developer | ZSoft Corporation |
| Format type | Run-length-encoded (RLE) raster bitmap (binary, lossless) |
| MIME type | image/x-pcx (also image/pcx, application/x-pcx) |
| Magic bytes | 0x0A at offset 0 (manufacturer byte); version byte at offset 1; encoding byte 0x01 (RLE) at offset 2 |
| Byte order | Little-endian |
| Header size | 128 bytes, fixed-length |
| Compression | PCX-RLE - lossless byte-oriented run-length encoding; uncompressed storage also permitted |
| Color depth | 1-bit mono, 4-bit (16-color), 8-bit indexed (256-color), 24-bit truecolor (3 planes × 8 bpp) |
| Color planes | 1-4 planes; bits-per-plane × plane count determines final color depth |
| Max dimensions | 65,535 × 65,535 pixels (16-bit Xmin/Xmax/Ymin/Ymax coordinate fields) |
| 256-color palette | Appended at end of file - 0x0C marker byte followed by 256 RGB triplets (769 bytes total; Version 5 only) |
| Version scheme | Header byte: 0x00 (v2.5), 0x02 (v2.8 with palette), 0x03 (v2.8 no palette), 0x04 (PC Paintbrush for Windows), 0x05 (v3.0+/24-bit) |
| DPI metadata | Horizontal and vertical DPI each stored as a 16-bit little-endian word in the header |
| Related container | .dcx - multi-page PCX bundle used for fax and document imaging |
| Released | 1985 (PC Paintbrush, ZSoft) |
| Latest version | Version 5 (header byte 0x05) - adds 24-bit truecolor and a 256-color VGA palette |
| Open standard | Yes · royalty-free |
| Specification | www.fileformat.info |
PCX conversions
Community Q&A
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