UUID Generator (v4)
Generate one or many random version-4 UUIDs in your browser with the cryptographic random source — nothing sent to a server.
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What a v4 UUID Is
A UUID is a 128-bit identifier written as 36 characters (8-4-4-4-12 hex). Version 4 fills 122 of those bits with cryptographically secure randomness — the collision odds are so small (you would need ~2.7×10¹⁸ UUIDs for a 50% chance of one duplicate) that they are treated as unique without any central registry. That is why they name database rows, API objects, files and devices everywhere.
Generation happens entirely in your browser via crypto.randomUUID(); nothing touches our server. The digit after the second dash is always 4 (the version), and the next group starts with 8, 9, a or b (the variant).
Frequently Asked Questions
Can two generated UUIDs collide?
Theoretically yes, practically never: with 2^122 possibilities, generating a billion UUIDs per second for 85 years gives ~50% odds of a single collision. Systems worldwide rely on this.
Should I use UUIDs as database primary keys?
They shine for distributed generation and non-guessable IDs, but random v4s fragment B-tree indexes. If insert performance matters, look at UUIDv7 (time-ordered) or ULID — same size, index-friendly.
Is v4 the only version?
No — v1/v6 embed a timestamp and MAC, v5 hashes a name, v7 is the newer time-ordered random format. v4 remains the default choice when you just need a random unique ID.
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UUID Generator (v4)