Are these UUIDs RFC 4122 compliant?

Yes. Version and variant bits match RFC 4122 (version 5, variant 1).

UUID v5 uses SHA-1 over namespace bytes + name bytes. It is deterministic but not intended for cryptographic signatures.

Does any data leave my device?

No. Everything runs locally in your browser.

Can I use a custom namespace?

Yes. Provide any valid UUID as the namespace. Built-in options include DNS, URL, OID, and X.500.

UUID v5 Generator (RFC 4122, Name-Based)

Create deterministic UUID v5 identifiers from a namespace and name. Private by design—nothing leaves your device.

Controls

Namespace

Name (string) Encoded as UTF-8 per RFC 4122.

Batch names

Output format

Prefix (optional)

Suffix (optional)

Colorize example view (legend below) Show hyphenated in preview

Output

Tip: Press Ctrl/Cmd + Enter to regenerate with the same settings.

Legend (hyphenated view):
XXXXXXXX = time_low
XXXX = time_mid
5XXX = time_hi_and_version (version = 5)
XX XX = clock_seq (variant in high bits)
XXXXXXXXXXXX = node

Understanding UUID v5

UUID v5 is a deterministic, name-based identifier defined by RFC 4122. It hashes a namespace UUID together with a name using SHA-1, then sets the version (5) and variant bits. The same namespace + name always yields the same 128-bit UUID, which makes v5 ideal for stable keys derived from URLs, domain names, or other strings.

How it works

We concatenate the 16 bytes of the namespace UUID with the UTF-8 bytes of the name, compute SHA-1, and take the first 16 bytes of the digest. We then set time_hi_and_version’s high nibble to 5 and apply the RFC 4122 variant (10xx) in clock_seq_hi_and_reserved, yielding xxxxxxxx-xxxx-5xxx-yxxx-xxxxxxxxxxxx.

Namespaces

Built-ins: DNS (6ba7b810-9dad-11d1-80b4-00c04fd430c8), URL (6ba7b811-9dad-11d1-80b4-00c04fd430c8), OID (6ba7b812-9dad-11d1-80b4-00c04fd430c8), X.500 DN (6ba7b814-9dad-11d1-80b4-00c04fd430c8). You can also provide a custom namespace UUID to define your own identifier space.

v1 vs v5 vs v3 vs v4 (quick guide)

v1 (time-based): Sorts by time; lightweight and widely compatible; uses clock sequence and node.
v5: Deterministic (SHA-1); preferred modern choice for name-based IDs.
v3: Deterministic (MD5); older, still interoperable but uses MD5.
v4: Random; best when you want unpredictability and no dependence on names.

Note: SHA-1 here is used for identifiers, not cryptographic signatures.