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UUID

UUID (Universally Unique Identifier) is a 128-bit identifier designed to be unique without central coordination. With 5.3 × 10^36 possible combinations, the collision probability is so low that you can generate millions of UUIDs per second for centuries without duplicates.

Examples

  • UUID v4: 9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d (completely random)
  • UUID v7: 018e8c4e-1a2b-7c3d-8e4f-9a0b1c2d3e4f (timestamp-sortable)
  • Postgres: CREATE TABLE users (id UUID PRIMARY KEY DEFAULT gen_random_uuid());

FAQ

Can UUIDs collide?

Theoretically yes, but with astronomically low probability. In UUID v4 you would need to generate 2.71 × 10^18 UUIDs to have a 50% chance of collision. In practice it's impossible.

Are UUIDs slower than integers in databases?

UUID v4 yes, due to index fragmentation. UUID v7 solves this by being sortable, achieving similar performance to BIGSERIAL in Postgres with the advantages of distributed generation.

Can I use UUIDs as authentication tokens?

Technically yes, but not recommended. For session tokens or API keys use specific generators with more entropy (256+ bits) and consider adding a prefix to identify token type.

Related generators

🆔 UUID generator Generate random UUIDs (v4 and v7), one or in bulk. Compatible with databases, APIs and testing. Runs entirely in your browser. 🎲 Random string generator Generate random strings with any alphabet: letters, numbers, symbols or a custom set. Ideal for tokens, slugs and test data.