UUID v5 generator

The snippets below hash the RFC 9562 Appendix A.2 DNS namespace with name www.example.com. CPython uuid.uuid5 is the named stdlib API. Node has no uuid.uuid5; crypto.randomUUID() is v4 only. The Node snippet uses crypto.createHash('sha1') — the same FIPS 180-4 SHA-1 this page runs through crypto.subtle.digest('SHA-1'). Both print 2ed6657d-e927-568b-95e1-2665a8aea6a2 (Appendix A.4). CPython 3.12+ python -m uuid -u uuid5 -n @dns -N www.example.com is that same uuid.uuid5() call — see UUID v5 in the shell. For how v5 compares to v4 and v7, see UUID Versions Explained: v4 vs v1, v5, v7 and v8 (Format & Length).

const { createHash } = require('crypto');

const ns = Buffer.from('6ba7b8109dad11d180b400c04fd430c8', 'hex');
const digest = createHash('sha1')
  .update(ns)
  .update('www.example.com', 'utf8')
  .digest();
digest[6] = (digest[6] & 0x0f) | 0x50;
digest[8] = (digest[8] & 0x3f) | 0x80;
const hex = digest.subarray(0, 16).toString('hex');
hex.slice(0, 8) + '-' + hex.slice(8, 12) + '-' + hex.slice(12, 16) + '-' + hex.slice(16, 20) + '-' + hex.slice(20)
// "2ed6657d-e927-568b-95e1-2665a8aea6a2"

import uuid

uuid.uuid5(uuid.NAMESPACE_DNS, 'www.example.com')
# UUID('2ed6657d-e927-568b-95e1-2665a8aea6a2')

Name bytes are the typed UTF-8 string, not a DNS lookup and not X.500 DER. This page and both snippets skip String.prototype.normalize / unicodedata.normalize, so NFC é and NFD é hash to ebfe0af8-3997-5ade-b634-ba92cf69f557 and 39004b7f-2a0b-588c-88f7-aa24552a7636. uuid.uuid3 is MD5 (v3) and is not offered here. crypto.randomUUID() belongs on the UUID v4 generator. SHA-1 is collision-broken; this is not a password hasher. For checksums, see SHA-256 vs SHA-1 vs MD5: Differences and Which to Use. For NFC before hashing, see Unicode normalize.

Generate on this page writes lowercase RFC 9562 §5.5 UUIDs with hyphens. SHA-1 via crypto.subtle.digest('SHA-1') runs over the 16 namespace octets plus TextEncoder UTF-8 name bytes. The first 128 bits become the UUID; version nibble 5 and variant 10xx overwrite those hash bits. util-linux uuidgen --sha1 calls uuid_generate_sha1(): the same SHA-1 of those 16 namespace bytes plus the --name C-string (UTF-8 in a UTF-8 locale), then version 5 / variant 10xx. The documented example uuidgen --sha1 --namespace @dns --name www.example.com prints 2ed6657d-e927-568b-95e1-2665a8aea6a2 (RFC 9562 Appendix A.4) — the same DNS + www.example.com pair this page documents. @dns is Appendix A.2 6ba7b810-9dad-11d1-80b4-00c04fd430c8. CPython 3.12+ python -m uuid -u uuid5 -n @dns -N www.example.com calls uuid.uuid5() and prints that same lowercase hyphenated Appendix A.4 UUID. Default python -m uuid is v4. These commands hash a namespace and name — they do not decode a pasted UUID.

uuidgen --sha1 --namespace @dns --name www.example.com
# 2ed6657d-e927-568b-95e1-2665a8aea6a2

uuidgen --sha1 --namespace 6ba7b810-9dad-11d1-80b4-00c04fd430c8 --name www.example.com
# same UUID; @dns is that Appendix A.2 value

uuidgen
# uppercase 8-4-4-4-12; version nibble is 4

uuidgen --sha1 --namespace @dns --name www.example.com
# unrecognized option

# Same DNS + www.example.com pair this page documents (Appendix A.4)
python -m uuid -u uuid5 -n @dns -N www.example.com
# 2ed6657d-e927-568b-95e1-2665a8aea6a2

# Custom namespace UUID; @dns is that Appendix A.2 value
python -m uuid -u uuid5 -n 6ba7b810-9dad-11d1-80b4-00c04fd430c8 -N www.example.com
# same UUID

# Missing -n or -N
python -m uuid -u uuid5
# Incorrect number of arguments. uuid5 requires a namespace and a name.

# 3.12 / 3.13 reject the batch flag
python -m uuid -u uuid5 -n @dns -N www.example.com -C 3
# unrecognized arguments: -C

Default uuidgen and uuidgen --random are UUID v4 — use the UUID v4 generator. uuidgen --time is v1. uuidgen --time-v6 is v6. uuidgen --time-v7 is v7 — use the UUID v7 generator. --md5 / -m is hash-based v3 and is not offered here. --hex / -x treats --name as hex bytes, not UTF-8 text — this page has no hex-name mode. --count is a time-based cache and is exclusive with --sha1 in current util-linux — it is not the CPython -C batch. Name bytes are the shell string / -N value, not a DNS lookup and not X.500 DER; no Unicode normalization is applied. An empty Name on this page hashes empty UTF-8; the CLI rejects a missing or empty -N. CPython 3.14+ python -m uuid -u uuid5 -n @dns -N www.example.com -C 3 reprints that same deterministic v5 three times; this page writes one UUID per Generate. Some 3.14 builds rejected a raw UUID as -n (invalid choice); 3.12 and later 3.14 accept one. This page's Custom field accepts any 8-4-4-4-12 UUID. Default python -m uuid is v4 — use the v4 generator. python -m uuid -u uuid1 is v1. python -m uuid -u uuid3 -n @dns -N www.example.com is MD5 (v3) and is not offered here. -u uuid6, -u uuid7, and -u uuid8 are 3.14+; -u uuid7 belongs on the v7 generator. This page's Uppercase and Remove hyphens options are display-only; neither uuidgen nor python -m uuid has a hyphen-strip flag — use tr -d '-' for 32 hex digits. print() adds a newline after the UUID. PowerShell [guid]::NewGuid().ToString() is lowercase hyphenated v4, not v5. Windows has no uuidgen --sha1 unless WSL. Version details are in UUID Versions Explained: v4 vs v1, v5, v7 and v8 (Format & Length).