Count must be a whole number of at least 1
- Why:
- A fractional or zero count. The generator produces discrete values.
- Fix:
- Enter a whole number between 1 and 1000.
API & Security
UUID Generator (v4)
Generate up to 1,000 version 4 UUIDs at once. Values come from your browser’s cryptographic random number generator, not from a server.
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This tool runs entirely in your browser. Your input is never uploaded, stored or logged.
How it works
A version 4 UUID is 128 bits, of which 122 are random. Six bits are fixed: four identify the version and two identify the variant, which is why the thirteenth hex digit is always 4 and the seventeenth is always 8, 9, a or b.
The random bits come from your browser’s cryptographic generator — crypto.randomUUID where available, and crypto.getRandomValues otherwise. Neither is Math.random, which is seeded predictably and must never be used for identifiers that end up in a database or a URL.
With 122 random bits, collisions are not a practical concern: you would need to generate billions of UUIDs before the probability became worth thinking about. The real trade-off is not uniqueness but ordering — random values arrive in no particular sequence, which scatters writes across a B-tree index. Where insert order matters, UUIDv7 or a ULID keeps the uniqueness and adds a time prefix.
Common problems
Every example below is run against this tool in our test suite, so what it says here is what the tool actually does.
Frequently asked questions
- Are these UUIDs safe to use as database keys?
- Yes. Version 4 UUIDs are 122 bits of randomness from a cryptographically secure source, so collisions are not a practical concern. Note that random UUIDs can fragment B-tree indexes; UUIDv7 or ULIDs are better where insert ordering matters.
- Are the UUIDs generated on your server?
- No. They are generated in your browser using the Web Crypto API. Nothing is transmitted, stored or logged.
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