What is the DCX file format?
A .dcx file is a multi-page image container developed by ZSoft Corporation as an extension of their PCX bitmap format. Where a standard .pcx holds a single image, a .dcx bundles up to 1,024 individual PCX pages into one file, making it well-suited for multi-page fax transmission and scanning workflows that were common in the early 1990s.
The file begins with a 4-byte magic number (B1 68 DE 3A) followed immediately by an index table of up to 1,023 four-byte little-endian offsets - one per embedded PCX image - terminated by a 00 00 00 00 entry. Each embedded page is a complete, self-contained PCX file with its own 128-byte header and PackBits run-length-encoded scan lines. Intel incorporated the DCX format into its FaxON/2 and related PC fax board software, which helped popularize it for document faxing at 1,728 × 2,200 pixel resolution (CCITT Group 3 standard).
Color depth follows the embedded PCX pages: typically 1 bpp monochrome for fax use, though 8 bpp (256-color) and theoretically 24 bpp pages are possible. The format carries no encryption or checksums and has no versioning - the specification is a single, frozen definition.
DCX is now effectively obsolete. TIFF (particularly TIFF-G4) became the standard for archived fax images, and PDF dominates multi-page document workflows. IrfanView and XnView MP can still open .dcx files for legacy data recovery.
Security & safety
RISK: LOWDCX is a legacy raster image container. Malformed files could trigger parser bugs in old software, but no known active exploits. Low risk with modern viewers.
Format details
in a nutshell- Visual FoxPro Database Compound Index - Visual FoxPro used .dcx for compound index files (database technology, not images); unrelated binary format.
- FoxPro for MS-DOS Database Index - Earlier FoxPro (pre-Visual FoxPro) also used .dcx for dBASE-compatible compound index files.
Programs that open DCX files
Windows3 apps
Visual FoxPro
Paid Only for the FoxPro .dcx compound index files (unrelated to PCX-based DCX). Visual FoxPro itself is EOL (Microsoft ended mainstream support 2007, extended support 2015). 
IrfanView
Free File > Open - IrfanView supports DCX multi-page PCX; use View > Multipage Images to navigate pages. 
Technical details
deep spec| Encoding | Binary |
| Byte order | Little-endian (x86 origin) |
| Magic bytes | `B1 68 DE 3A` at offset 0 |
| Index table | Up to 1,023 × 4-byte little-endian page offsets immediately after the magic bytes; terminated by `00 00 00 00` |
| Maximum pages | 1,024 embedded PCX images per DCX file |
| Embedded page format | Each page is a complete, self-contained PCX file with its own 128-byte header and PackBits-compressed scan lines |
| Compression | PackBits RLE per row within each embedded PCX page (inherited from the PCX format) |
| Color depth | 1 bpp monochrome typical (fax use); up to 8 bpp (256-color) or 24 bpp for color PCX pages |
| Fax page resolution | 1,728 × 2,200 pixels per page (CCITT Group 3 standard fax resolution) |
| Max page dimensions | 65,535 × 65,535 pixels per page (inherited from PCX Version 5 16-bit header fields) |
| Typical file size | 10 KB - 5 MB (depends on page count and image complexity) |
| MIME type | image/x-dcx |
| Released | Late 1980s (ZSoft PC Paintbrush era); popularized ca. 1991 for Intel fax boards |
| Latest version | Single specification; no versioned revisions documented |
| Open standard | Yes · royalty-free |
| Specification | help.accusoft.com |
DCX conversions
Community Q&A
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