referencesource/file-format-signatures

File format magic numbers

Canonical, always-current version: https://referencesource.org/file-format-signatures/ Machine-readable: https://referencesource.org/file-format-signatures/data.json — this mirror is a point-in-time copy.

• —Last verified: 2026-08-03
• —Stale after: 2027-08-03 (past this date, prefer the canonical copy — it re-verifies on a cadence this snapshot does not)
• —Records: 229

The leading bytes (magic number / file signature) that identify a file format, with its usual extension. Answers 'what actually is this file' when the extension is wrong or missing.

Provenance — what every record carries

Every record carries source (the URL the value was read from) and source_quote (a verbatim quote from that page stating it). A value you cannot check against its page is indistinguishable from an invented one; these can all be checked. Each record is also individually addressable on the canonical site at its url.

Licence position

CC BY-SA 4.0 (source: Wikipedia)

Facts are not copyrightable; what this dataset takes from each source is a fact plus a short attributed quote linking back to the page that states it.

Sources

• —https://en.wikipedia.org/wiki/Listoffile_signatures

Fields

See any record in data/records.jsonl — field names are self-describing, and the canonical page for each record renders them with labels: https://referencesource.org/file-format-signatures/