How to generate UUID v4
- Enter how many UUIDs you need, from 1 to 10,000.
- Choose the format: lowercase with hyphens (standard), uppercase, without hyphens (32 hex characters), with braces, or quoted with a trailing comma for pasting into code, JSON or SQL.
- Press Generate, then copy the list or download it as a text file.
About version 4 UUIDs
A UUID v4 is a 128-bit identifier in which 122 bits are random. The other six bits mark the version (the 13th hex digit is always 4) and the variant (the 17th digit is 8, 9, a or b). With 2122 possible values, the chance of two randomly generated v4 UUIDs colliding is so small it can be ignored in practice.
That makes v4 the default choice for database keys, request and correlation IDs, file names, idempotency keys and test fixtures. The values here come from crypto.randomUUID(), the browser's cryptographically secure generator, so they are unpredictable and safe to use where guessing an ID would be a problem.
If you use UUIDs as primary keys in a large database table, consider UUID v7, which is time-ordered and keeps indexes efficient. Everything is generated locally; no IDs are sent to or stored on a server.
FAQ
How do I generate a UUID in code?
JavaScript: crypto.randomUUID(). Python: str(uuid.uuid4()). Java: UUID.randomUUID(). PostgreSQL: gen_random_uuid(). Linux: uuidgen.
Are UUID v4 values truly unique?
They are random, not guaranteed unique, but a collision is astronomically unlikely: you would need around 2.7 quintillion UUIDs for a 50% chance of one duplicate.
Can I check whether a value is a valid UUID?
Yes. Paste it into the Inspect box below the generator to see its version and variant.