A UUID (Universally Unique Identifier) is a 128-bit identifier that can be generated anywhere, by anyone, at any time — with no central authority and no realistic chance of collision. That property makes UUIDs the default choice for database primary keys in distributed systems, request tracing IDs, file names in object storage, and any situation where two machines must mint identifiers independently.
This generator produces version 4 UUIDs, which are built from cryptographically random numbers. Generate one or dozens at a time and copy them straight into your database seeds, configuration files, or test fixtures.
How to Use This Tool
- Choose how many UUIDs you need.
- Click generate — each UUID is created with the browser's cryptographic random source.
- Copy individual UUIDs or the whole list.
- Use them as primary keys, API keys' public parts, or trace identifiers.
Frequently Asked Questions
Can two generated UUIDs ever collide?
Version 4 UUIDs contain 122 random bits, giving about 5.3 undecillion possible values. You would need to generate roughly a billion UUIDs per second for 85 years to reach a 50% collision probability — in practice, collisions never happen.
What do the digits in a UUID mean?
A v4 UUID like xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx is almost entirely random. The '4' marks the version, and the 'y' position encodes the variant (8, 9, a, or b). Everything else is random hex.
Should I use UUIDs or auto-increment integers as database keys?
UUIDs win when records are created across multiple servers, must be unguessable, or need to be generated before insertion. Auto-increment integers are smaller and index faster on a single database. Many teams use both: an integer internally, a UUID publicly.