UUID generator
Random version 4 UUIDs, one or up to fifty at a time.
Free, no sign-up.
UUID generator
How a version 4 UUID is built
A UUID is 128 bits written as 32 hexadecimal digits in groups of 8, 4, 4, 4 and 12. In a version 4 UUID, 122 of those bits are random. The rest mark the type: the first digit of the third group is always 4, and the first digit of the fourth group is 8, 9, a or b. These come from your browser's cryptographic random generator.
Duplicates are not a practical worry. You would need to make about 2.7 quintillion (2.7 × 10^18) of them before the chance of any two matching reaches one in two.
Version 4 or version 7?
Version 4 is the right choice for IDs that should reveal nothing. As database keys, though, random IDs land all over an index. Version 7, standardized in 2024, starts with a timestamp so new IDs sort in order, at the cost of revealing roughly when each was made. This page makes version 4.
More developer tools
- Base64 encode and decode: Decode Base64 to text, or encode text as standard or URL-safe Base64.
- URL encode and decode: Make text safe for a URL, or turn percent-encoded text back into words.
- JSON formatter: Check JSON, see where it breaks, then format it for reading or minify it.
- JWT decoder: Read a JSON Web Token’s header, claims and times without sending it anywhere.
- SHA-256 hash: The SHA-256 digest of any text as you type, with SHA-1, SHA-384 and SHA-512 beside it.
- Token generator: Secure random strings for keys, secrets and test data.
- All developer tools on one page
Generate random version 4 UUIDs for database keys, test data or request IDs. They come from your browser’s cryptographically secure random generator, up to 50 at a time, one per line.
How it works
- Choose how many — From 1 to 50.
- Generate — Each press makes a fresh set.
- Copy them — One per line, ready to paste.
Examples
- A version 4 UUID — Looks like 3f2b8c1e-9a4d-4c7b-8e2f-6d1a0b5c9e47: the 4 marks the version
FAQ
- Can two be the same? — In practice no: there are 2^122 possible random version 4 UUIDs.
- Uppercase or lowercase? — Lowercase, the standard form; UUIDs compare the same either way.
- Are they stored? — No. They are made in your browser and never sent anywhere.