7-Zip signature (37 7A BC AF 27 1C)

A 7-Zip archive begins with the 6-byte signature '7z' (0x37 0x7A) followed by the fixed bytes 0xBC 0xAF 0x27 0x1C, then a 2-byte format version.

file signature

magic: 37 7A BC AF 27 1C @ offset 0

ascii: 7z\xbc\xaf'\x1c

.7z application/x-7z-compressed

spec: 7z archive format

Bytes 0-1: '7z' (37 7A). Bytes 2-5: fixed BC AF 27 1C.
Bytes 6-7: format version (e.g. 00 04).
Followed by a start-header CRC and a pointer to the end header that holds the actual archive metadata.

source: https://py7zr.readthedocs.io/en/latest/archive_format.html
version: 7z archive format documentation (signature header '7z\xbc\xaf\x27\x1c')
retrieved: 2026-05-29 · updated: 2026-05-29T00:00:00Z

per-fact attribution:

ext.magic_hex — https://py7zr.readthedocs.io/en/latest/archive_format.html Signature header: kSignature = '7z' 0xBC 0xAF 0x27 0x1C, then 2-byte ArchiveVersion.
ext.magic_hex — https://en.wikipedia.org/wiki/List_of_file_signatures Corroborates 37 7A BC AF 27 1C as the 7-Zip signature.

agent: curl -H 'accept: application/json' wire.phall.io/magic/7z or /magic/7z.json