UUID Generator

Generate universally unique identifiers (UUIDs, also called GUIDs) that follow RFC 9562 — the standard that replaced RFC 4122. Pick a version, choose how many you need, and copy or download the result. Everything is computed in your browser with a cryptographic random number generator.

How to use it

1. Choose a version. If you are not sure, v4 is the right default.
2. For v5, fill in a namespace UUID and a name — the same pair always produces the same identifier.
3. Set how many you want (up to 100) for the random versions.
4. Tick Uppercase if your system expects A4018DCB-… rather than a4018dcb-….
5. Click Generate UUID, then copy the value or download the list as a text file.

Which UUID version should I use?

v4 — random

122 random bits. No timestamp, no machine identity, nothing to leak. It is the version almost everyone means when they say "a UUID", and the safest default for public identifiers.

v7 — time-ordered

A 48-bit Unix millisecond timestamp followed by random bits, so v7 values sort in creation order as plain text or as a database key. This is the modern recommendation for primary keys: a v4 primary key scatters writes across a B-tree index, while v7 keeps inserts at the end of it. Values generated in the same millisecond carry a counter, so a batch stays in order.

v5 — namespace + SHA-1 (deterministic)

SHA-1(namespace + name), truncated to 16 bytes. Feed it the same namespace and the same name and you get the same UUID forever, on any machine — useful for deriving a stable ID from a URL, a domain, or a filename. The four namespaces defined by the RFC (DNS, URL, OID, X.500) are listed under the namespace field. Note that v5 is a derivation, not a secret: anyone with the name and namespace can recompute it.

v1 — time-based

A 60-bit timestamp plus a node identifier. Classic, but it embeds when the value was made. Because reading a real MAC address in the browser is impossible (and would be a privacy leak), the node here is random with the multicast bit set, exactly as the RFC prescribes for generators without hardware access.

Nil UUID

00000000-0000-0000-0000-000000000000 — the all-zero UUID, used as a null placeholder.

Frequently asked questions

Are UUID and GUID the same thing?

Yes. GUID is Microsoft's name for the same 128-bit identifier and the same textual format. A UUID generated here works anywhere a GUID is expected.

Can two UUIDs collide?

Not in practice. A v4 UUID has 122 random bits — you would need to generate billions per second for a century before a collision became likely.

Is a UUID safe to use as a password or API token?

No. A UUID is an identifier, not a secret: it is meant to be visible in URLs and logs, and v1/v5/v7 are partly predictable. Use the password generator or the token generator for anything secret.

Why are these random values trustworthy?

They are drawn from crypto.getRandomValues (via node:crypto on the server), the platform's cryptographically secure random number generator — never Math.random().

Privacy

Every UUID is generated locally, in your browser. Nothing is sent to a server, nothing is logged, and nothing is stored. Because generated identifiers are treated as sensitive output, they are never included in a shareable link — only your settings are.