Choose how many you need. UUIDs are generated locally with crypto.randomUUID.
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UUIDs in one paragraph
A UUID (universally unique identifier), also called a GUID, is a 128-bit value used to label something without a central authority handing out numbers. Version 4 is almost entirely random (122 of the 128 bits), so two independently generated values practically never collide. That property makes them handy for database primary keys, request IDs in logs, file names, message IDs and idempotency keys.
Anatomy of a v4 UUID
3f2504e0-4f89-41d3-9a0c-0305e82c3301— 32 hexadecimal digits in 8-4-4-4-12 groups. The 4 at the start of the third group is the version; the first digit of the fourth group (8, 9, a or b) is the variant. The rest is random.
How they're generated here
Each UUID comes from crypto.randomUUID(), which draws from your operating system's cryptographically secure random source, entirely in your browser. Nothing is sent anywhere, so you can generate as many as you need for test data, migrations or seed files.
A 128-bit identifier where 122 bits are random. Written as 32 hex digits in 8-4-4-4-12 groups, e.g. 3f2504e0-4f89-41d3-9a0c-0305e82c3301. The chance of two colliding is negligible for any realistic number of IDs.
Are these safe to use as database keys?
Yes, that is a common use. They can be generated anywhere without coordination. The trade-off versus auto-increment integers is size and index locality.
How random are they?
They use crypto.randomUUID(), which draws from the operating system's cryptographically secure random source.
Is a UUID a secret?
A version-4 UUID has 122 random bits, so it is effectively unguessable — but it is designed for uniqueness, not secrecy, and it often appears in URLs and logs. It's fine as a hard-to-enumerate identifier; don't rely on it alone as the only thing protecting a sensitive resource.
How likely is a collision?
Negligible for any realistic scale. You would need to generate about 2.7 quintillion UUIDs to have a one-in-a-billion chance of a single duplicate. In practice, treat version-4 UUIDs as unique.
UUID vs auto-increment integer for a database key?
UUIDs can be generated anywhere without coordinating with the database, which suits distributed systems, offline clients and merging data sets. The trade-offs are size (16 bytes vs 4–8) and worse index locality with fully random v4; UUIDv7 (time-ordered) addresses the locality issue if your database supports it.
What's the difference between the UUID versions?
v1 is time + MAC address based (leaks info, mostly avoided). v4 is random (the common default, what this tool generates). v5 is a hash of a namespace + name (deterministic). v7 is time-ordered random, better for database keys. For a generic unique ID, v4 is the right choice.
Last reviewed: September 2026. Figures and formulas are checked against their published sources; see the site's data notes.