Generators

UUID Generator

Generate random v4 UUIDs or name-based v5 UUIDs. Copy in standard, URN, or hex format.

Click Generate to create a UUID
Output Formats
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URN format
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Hex format (no dashes)
Generation History
No history yet.

How to use this tool

  1. On the Version 4 (Random) tab, click Generate to create a new random v4 UUID — one is also generated for you when the page loads.
  2. Copy it in your preferred format using Copy next to the UUID, or the Copy buttons under URN format and Hex format (no dashes).
  3. For a deterministic UUID, switch to the Version 5 (Name-Based) tab and pick a namespace from the dropdown.
  4. Type a name into the Name field and click Generate v5 — the same namespace + name always produces the same UUID.
  5. Choose Custom UUID in the namespace dropdown to supply your own namespace UUID instead of the built-in DNS, URL, OID, or X.500 values.
  6. Re-copy any recent result from Generation History, which keeps your last five UUIDs.

Why this tool is helpful

Generate unique IDs instantly

v4 UUIDs carry 122 bits of randomness, so collisions are effectively impossible. Great for database primary keys, object IDs, and session tokens.

Create reproducible identifiers

v5 UUIDs are deterministic — the same namespace + name always yields the same UUID, so you can derive a stable ID from a known string.

Match the format your system expects

Copy the standard dashed form, an RFC 4122 urn:uuid: URN, or raw 32-digit hex without dashes — whatever your code or schema needs.

Use standards-compliant namespaces

Built-in DNS, URL, OID, and X.500 namespaces follow RFC 4122, so name-based UUIDs are interoperable across languages and platforms.

Populate test data & fixtures

Quickly produce realistic UUIDs for mocks, seed data, and API testing without writing a helper script.

Stay private

Everything runs in your browser. Nothing you type is uploaded, logged, or sent to a server.

FAQ

What's the difference between v4 and v5 UUIDs?

Version 4 is fully random — 122 bits of randomness with the version and variant bits set. Version 5 is name-based and deterministic: it hashes a namespace UUID plus a name with SHA-1 and keeps the first 128 bits.

How random is a v4 UUID?

It's generated with crypto.getRandomValues, the browser's cryptographically secure random source. With 122 random bits, the chance of a collision is negligible even across billions of IDs.

Why does the same name always give the same UUID?

v5 UUIDs are computed deterministically: SHA-1 is applied to the namespace UUID bytes followed by the name, then the version and variant bits are set. Identical inputs always produce an identical output.

Which namespace should I choose?

It depends on what the name represents. Use DNS for domain names, URL for URLs, OID for object identifiers, X.500 for distinguished names, or Custom UUID to supply your own.

What are the URN and hex formats?

The URN format prefixes the UUID as urn:uuid:…. The hex format is the same UUID with all dashes removed, giving a raw 32-character hexadecimal string. Both represent the identical identifier.

Are UUIDs guaranteed to be unique?

Not mathematically guaranteed, but a v4 UUID's collision probability is effectively zero in practice. v5 UUIDs are unique per namespace + name pair by construction.

Does any of my data leave my browser?

Never. All generation happens locally in JavaScript. Your names and UUIDs are not sent to, stored on, or logged by any server.