What it does
A UUID (universally unique identifier, also called a GUID) is a 128-bit label written as 32 hex digits in five groups, like f47ac10b-58cc-4372-a567-0e02b2c3d479. Programs use them as IDs because anyone can make one without a central list, and two will almost never match.
This page makes them with your browser’s secure random number generator and checks UUIDs you paste in. Nothing is sent or stored. A version 7 UUID carries the time it was made; read such times with the timestamp converter, and pull UUIDs out of a log with the regex tester.
How to use it
- Pick a version and how many you want (1 to 500). A list appears at once.
- Tick UPPER CASE or No hyphens if the place you paste them into needs that.
- Press Copy all or Download .txt (one UUID per line). Generate new makes a new list; Clear empties it.
- To check one, paste it under “Check a UUID”.
What each setting does
- v4: random: 122 random bits. The usual choice.
- v7: time-ordered: starts with the time in milliseconds since 1970, then random bits, so a list sorts in the order it was made.
- UPPER CASE: changes a-f to A-F. Both mean the same.
- No hyphens: writes the 32 digits without dashes.
- Check a UUID: accepts hyphens, no hyphens, braces
{...}orurn:uuid:. It reads the version digit (the first digit of the third group) and the variant digit (the first of the fourth group, which must be 8, 9, a or b). For a version 7 UUID it also shows when it was made, in UTC.
Worked example
Make 10 v4 UUIDs: all 10 are different, each has 4 as the first digit of its third group and 8, 9, a or b as the first digit of its fourth. Switch to v7: the third group now starts with 7 and the list is already in sorted order. Paste f47ac10b-58cc-4372-a567-0e02b2c3d479 into the checker: it says “Valid: version 4 (random)”.
FAQs
Can two UUIDs ever be the same? In theory yes; in practice no. You would need to make billions of v4 UUIDs before a repeat became even slightly likely.
Is a UUID a password? No. A v7 UUID shows when it was made, so do not use UUIDs as secret tokens.
Where the numbers come from
- UUID layout, versions and variant: IETF RFC 9562 (2024), which replaced RFC 4122. fibub's own working.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-10.