UUID Generator
Generate random UUID v4 identifiers instantly. Copy single UUIDs or generate bulk UUIDs for testing and development.
Generates random UUID v4 (Universally Unique Identifier) using the browser's built-in crypto.randomUUID() API.
How to Generate UUIDs
- 1
Set the count
Choose how many UUIDs you want to generate (1-100).
- 2
Generate UUIDs
Click the 'Generate' button to create new random UUIDs.
- 3
Copy individual UUIDs
Click the copy button next to any UUID to copy it to your clipboard.
- 4
Copy all UUIDs
Use the 'Copy All' button to copy all generated UUIDs at once.
UUIDs: what version 4 gives you
Anatomy of a v4 UUID
A UUID is 128 bits written as 32 hexadecimal digits in five groups, 8-4-4-4-12. In version 4, the first digit of the third group is always 4, and the first digit of the fourth group is 8, 9, a or b. The remaining 122 bits are random, which leaves about 5.3 undecillion possible values. These are produced by crypto.randomUUID() in your browser.
Will two ever collide?
In practice no. To have even a one in a billion chance of a single duplicate you would need to generate around 100 trillion UUIDs. The real risk is a bad random source, not the maths, which is why this page uses the browser's secure generator rather than Math.random. UUIDs are identifiers, not secrets: do not use one as the only protection for a private link.
Where they are used
Common uses are database primary keys created on the client before a row is saved, idempotency keys that stop a payment request being applied twice, file and upload names, correlation IDs in logs, and test fixtures. In .NET and SQL Server the same thing is called a GUID, and the text format is identical.
Storage and sorting caveats
Random UUIDs are inserted at random positions in an index, which can slow writes on large tables compared to sequential keys. If you need roughly time-ordered IDs, look at UUID version 7 or ULID, which this page does not generate. Store a UUID as a native uuid or 16-byte binary column where you can; as text it takes 36 bytes. Compare them case-insensitively, since both upper and lower case are valid.