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File Format
Name Zoo
Extension(s) .zoo
MIME Type(s) application/x-zoo
PRONOM x-fmt/269
Wikidata ID Q219983
Released 1986

Zoo is a compressed archive format developed by Rahul Dhesi. It was one of the many competing archive formats in the 1980s, and was based (originally) on LZW compression. It had some popularity with Open/VMS and Amiga systems, but didn't ultimately win out over ZIP.



The Zoo software encompassed several different utilities, which were sometimes distributed individually, and which had their own version numbers.

  • Zoo - The main program
  • Ooz - Extractor
  • Booz (Barebones Ooz) - Extractor; some versions can also list files
  • Looz (Ooz with List) - Extract/list/execute
  • Atoz - Helper utility for converting other formats (ARC, LBR) to Zoo
  • Fiz - Analyze damaged Zoo files
  • Stuff - File finder
  • Sez - Self-Extracting Zoo utility

Compression methods

ID Name Description
0 No packing Uncompressed
1 LZD LZW. A fairly generic LZW implementation, with a dynamic code size from 9 to 13 bits, and two special codes: 256=Clear, 257=Stop.
2 LZH LZ77+Huffman. Nearly identical to LHA's "lh5" method. A small difference is that Zoo defines a way to mark the end of data. The format is pretty well documented in the comments in unzoo.c by Martin Schoenert (see below).


Files have bytes DC A7 C4 FD at offset 20.

Zoo files typically start with "ZOO ?.?? Archive.", followed by the byte 0x1a, where each "?" is a digit. Regarding this field, the source code says "The contents of the text message are however not used by Zoo and they may be anything."

Related formats


[Ed. note: The Zoo format information in these documents is not of the highest quality. We haven't found a specification that is reasonably complete and correct.]


Original(?) source code:

Other source code and packages:

Sample files


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