UUID v5 generator — the same name always gives the same UUID

How to use the UUID v5 generator

1. Choose a Namespace: DNS, URL, OID, X.500 or Custom UUID.
2. For a custom namespace, paste it into Custom namespace UUID. Hyphens, braces, urn:uuid: and upper-case letters are accepted.
3. Type the Names (one UUID per line). Empty lines are skipped.
4. Pick the Version: v5 (SHA-1) or v3 (MD5).
5. Copy the list, or save the Name / UUID table as uuids.csv.

What it does and when to use it

Name-based UUIDs give you stable IDs without a database lookup. Hash the same natural key, such as a domain, a URL, an email or order-1001, and every service gets the same UUID. That helps when merging data from several systems or rerunning an import.

A good pattern is to make one random UUID for your application and use it as the custom namespace for all your own names.

To read the version, variant and timestamp of any UUID, paste it into the UUID inspector. For random v4 IDs, use the UUID generator. To see the SHA-1 and MD5 digests themselves, use the hash generator.

How it works

As defined in RFC 9562 (which replaced RFC 4122):

1. The namespace UUID is turned into its 16 bytes, and the name is encoded as UTF-8 and appended.
2. The bytes are hashed with SHA-1 (v5, using Web Crypto) or MD5 (v3, using the hash-wasm library, which loads on first use).
3. The first 16 bytes of the hash are kept. The high four bits of byte 6 are set to the version (5 or 3), and the top two bits of byte 8 are set to the RFC variant.
4. The result is written in the 8-4-4-4-12 hex form.

The standard namespaces are DNS 6ba7b810-9dad-11d1-80b4-00c04fd430c8, URL …b811…, OID …b812… and X.500 …b814…, with the rest of the UUID the same. Everything runs in your browser.

Worked examples

DNS namespace, name python.org. These are the values in Python’s own documentation:

v5: 886313e1-3b8a-5372-9b90-0c9aee199e5d
v3: 6fa459ea-ee8a-3ca4-894e-db77e160355e

The third group starts with the version digit (5372, 3ca4).

URL namespace, name https://example.com/products/42:

34adb0ec-5647-5afd-9b6d-76be74ef5892

An invalid custom namespace such as nope gives: A UUID is 32 hexadecimal digits, usually written 8-4-4-4-12 with hyphens.

Limits and tips

• Not secret, not random. Anyone who knows the namespace and name can recompute the UUID. Never use one as a token or password-reset key.
• Not sortable by time. Use v7 if insert order matters for your database index.