ZIP signature (PK\x03\x04)

A ZIP archive begins with a local file header whose signature is 'PK' (0x50 0x4B, the initials of Phil Katz) followed by 0x03 0x04. Empty archives and some variants start with the central-directory (PK\x01\x02) or end-of-central-directory (PK\x05\x06) signatures.

file signature

magic: 50 4B 03 04 @ offset 0

ascii: PK\x03\x04

.zip.jar.docx.xlsx.pptx.odt.epub.apk application/zip

spec: PKWARE APPNOTE.TXT .ZIP File Format Specification

Signatures are 32-bit values stored little-endian: local file header 0x04034b50 => 50 4B 03 04.
Empty archive: 'PK\x05\x06' (50 4B 05 06, end of central directory).
Spanned/split markers use 'PK\x07\x08' (50 4B 07 08).
Many formats are ZIP containers and share this magic: JAR, DOCX/XLSX/PPTX (OOXML), ODT (ODF), EPUB, APK. Disambiguation requires inspecting the archive contents (e.g. mimetype entry, META-INF).
The 'PK' bytes are the initials of Phil Katz, author of PKZIP.

provenance

source: https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT
version: PKWARE APPNOTE.TXT, .ZIP File Format Specification, 4.3.7 (local file header signature 0x04034b50)
retrieved: 2026-05-29 · updated: 2026-05-29T00:00:00Z

per-fact attribution:

ext.magic_hex — https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT Local file header signature is 0x04034b50, stored little-endian => bytes 50 4B 03 04 ('PK\x03\x04').
ext.notes — https://en.wikipedia.org/wiki/List_of_file_signatures Corroborates PK\x03\x04 / PK\x05\x06 / PK\x07\x08 ZIP signatures and the shared-base-format note (jar, docx, xlsx, odt, epub, apk all ZIP containers).

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

ZIP signature (PK\x03\x04)

file signature

provenance

see also