// generate v1, v4, v5 uuids · bulk generation · copy all · nothing leaves your browser
generated uuids
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in computer systems. They're written as 32 hexadecimal digits in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. The probability of generating two identical UUIDs is astronomically small.
Which version should I use?
v4 — random, most common, use for most cases
v1 — time-based, includes timestamp and MAC address
v5 — name-based using SHA-1, deterministic (same input = same UUID)
Frequently Asked Questions
Are these UUIDs truly unique?+
v4 UUIDs use cryptographically secure random numbers via the browser's crypto.randomUUID() API. The chance of a collision is 1 in 5.3×10³⁶ — effectively impossible in practice.
What's the difference between UUID and GUID?+
Nothing meaningful — GUID (Globally Unique Identifier) is Microsoft's name for the same standard. They're interchangeable in practice and follow the same format.
When should I use v5 over v4?+
Use v5 when you need the same input to always produce the same UUID — for example, generating a consistent ID for a URL or username across different systems. Use v4 when you just need a random unique ID.