What is the DIZ file format?
Files with the .diz extension store information on ZIP archive contents. A .diz file is plain text in 7-bit ASCII, kept deliberately short: the convention limits it to at most 10 lines, each no longer than 45 characters. This ceiling - roughly 450 bytes - makes the description easy to display in any terminal-width listing.
Originally the .diz extension was used exclusively for files named FILE_ID.DIZ, which became popular on BBS (Bulletin Board Systems) in the early 1990s, when the Internet was still emerging. The convention was devised by Richard Holler for the PCBoard BBS software and spread quickly across file-distribution networks. BBS software read FILE_ID.DIZ automatically when a file was uploaded or listed, giving administrators and users a standardised description without opening the archive. Nowadays .diz files continue to ship inside freeware and shareware ZIP archives, and some legacy or indie software releases still follow the same convention. Unlike the related .nfo format - which may span many lines and include CP437/ANSI artwork - a .diz file stays plain ASCII with no colour or decoration. Because it is plain text, any text editor or even a web browser can open a .diz file directly. .diz files carry only descriptive text and contain no executable data needed for the application to run.
Security & safety
RISK: LOWA FILE_ID.DIZ is plain text and cannot execute - reading it is completely safe. The only context risk is what it came packaged with: DIZ files often live inside vintage shareware, abandonware or scene archives, and the SOFTWARE in that archive (cracks, keygens, old installers) may be unsafe. The description file itself is harmless.
Format details
in a nutshellPrograms that open DIZ files
Windows3 apps
Windows Notepad
Built-in Right-click > Open with > Notepad to read the description instantly. It's plain text. 
Notepad
Open-source Open the .diz; use a monospace font so the 45-column layout lines up as intended. 
GetDiz
Free A free DIZ/NFO viewer named after this format - opens FILE_ID.DIZ (and NFO art) with the right fixed-width font. 
macOS2 apps
TextEdit
Built-in Open the .diz as plain text (Format > Make Plain Text if it opens rich); a monospace font keeps the alignment. 
BBEdit / TextWrangler
Freemium Open as plain text in a fixed-width font. (TextWrangler is discontinued; BBEdit's free mode replaces it.) 
Linux1 app
gedit / nano / any text editor
Open-source Open the .diz as text. A monospace font preserves the 45-column wrapping.
Any browser / text viewer
Free Drag FILE_ID.DIZ into a browser tab or any online text viewer to read it - no install needed. Technical details
deep spec| Character encoding | 7-bit plain ASCII - no ANSI colour sequences, no CP437 art, no multi-byte characters |
| MIME type | text/plain |
| Maximum line count | 10 lines (enforced by convention; BBS software relied on this limit when displaying file listings) |
| Maximum characters per line | 45 characters per line (terminal-width convention inherited from the BBS era) |
| Typical file size | Under 450 bytes (10 lines × 45 characters + line endings) |
| Canonical file name | FILE_ID.DIZ - the archive must contain a file with exactly this name for BBS software to auto-detect it |
| Archive placement | Stored in the root directory of the distribution ZIP archive, not in a subfolder |
| Binary signature (magic bytes) | None - identified by file name (FILE_ID.DIZ) and plain-text content, not by a byte signature |
| Line-ending convention | CR+LF (0x0D 0x0A) - inherited from DOS/BBS tradition; modern editors accept any line ending |
| Automated BBS detection | PCBoard, TBBS, RemoteAccess, and similar BBS platforms parsed FILE_ID.DIZ automatically on file upload and listing |
| Distinction from .nfo | .nfo files have no line-length limit and may contain CP437/ANSI artwork; .diz is intentionally short and art-free |
| Origin | Devised by Richard Holler for Clark Development's PCBoard BBS software in the early 1990s shareware ecosystem |
| OS compatibility | OS-independent plain text; originated on DOS, used unchanged on Windows, macOS, and Linux |
| Common companion files | Often bundled in the same archive alongside .nfo (release notes) and .sfv (checksum verification) files |
| Released | Early 1990s (BBS / shareware distribution era) |
| Latest version | Convention unchanged since the 1990s; no formal version |
| Open standard | Yes · royalty-free |
| Specification | en.wikipedia.org |
DIZ conversions
Community Q&A
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