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UUID Generator

Generate cryptographically random UUID v4 identifiers in bulk, formatted exactly how your code needs them.

Formatting

What a UUID is for

A UUID (universally unique identifier) is a 128-bit value you can generate anywhere, on any machine, without asking a central authority, and still be confident it will never clash with another. That property makes them the default primary key for distributed systems, the id you stamp on a new record before it reaches the database, the token in an idempotency header, and the name of a file that must not overwrite anyone else's.

The v4 format, digit by digit

Version 4 is the random flavour and by far the most common. It looks like xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx: 32 hex digits in 8-4-4-4-12 groups. The 4 in the third group is fixed as the version marker, and the first digit of the fourth group is always 8, 9, a or b (the variant). Everything else is random, giving 122 bits of entropy - enough that you can treat collisions as impossible in practice.

Handy formatting options

  • Uppercase - some legacy Microsoft systems and older APIs expect GUIDs in capitals.
  • No hyphens - a compact 32-character string that fits neatly into URLs and filenames.
  • Quoted and comma-separated - paste a ready-made list straight into a code array or a SQL IN (...) clause.

Need other developer utilities? Try the hash generator for checksums, the password generator for secure secrets, or the random number generator when a full UUID is overkill.

Frequently asked questions

What is a UUID v4?
A UUID v4 is a 128-bit identifier where almost all of the bits are random. It is written as 32 hexadecimal digits in five hyphen-separated groups, like 3f2504e0-4f89-41d3-9a0c-0305e82c3301. The 13th digit is always 4 (the version) and the 17th is one of 8, 9, a or b (the variant).
Are these UUIDs really random and unique?
Yes. They are generated with crypto.randomUUID, which draws on the browser cryptographic random source rather than Math.random. A v4 UUID has 122 random bits, so the chance of two colliding is vanishingly small - you would need to generate billions per second for many years before a collision became likely.
Do the UUIDs get sent to a server?
No. Everything is generated locally in your browser. Nothing is logged, stored or transmitted, so the identifiers are safe to use for anything, including secrets and database keys.
Should UUIDs be uppercase or lowercase?
The RFC 4122 standard outputs lowercase and treats letters case-insensitively, so lowercase is the safe default. Some systems (older Microsoft GUIDs, for instance) prefer uppercase. Use the uppercase toggle if your target system expects it.
What is the difference between a UUID and a GUID?
Practically nothing. GUID (Globally Unique Identifier) is Microsoft name for the same 128-bit value. A v4 UUID and a random GUID are interchangeable; the only differences you will meet are formatting conventions like casing and braces.

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