How to use it
- Choose the Kind: version 4 for random identifiers, or version 7 or ULID for identifiers that sort by time.
- Set How many to a number from 1 to 1000.
- Tick Upper case or Wrap in braces if your system needs them.
- Use Copy to copy the list, or Download to save it as a text file with one identifier on each line.
UUID and ULID formats
A UUID is 128 bits written as 32 hexadecimal digits in five groups of 8-4-4-4-12, such as 3f2b8c1e-7a9d-4f3e-9b21-6d5e4c3b2a10. The version digit shows the kind, and the variant bits show that the RFC layout applies. A ULID is 128 bits written as 26 characters of Crockford base32, such as 01ARZ3NDEKTSV4RRFFQ69G5FAV.
UUID version 4: 122 random bits
UUID version 7: 48 bits of time and 74 more bits
ULID: 48 bits of time and 80 random bitsVersion 7 and ULID sort by time
Both start with the Unix time in milliseconds, so an identifier made later sorts after one made earlier, which keeps database indexes fast. Within one batch, identifiers made in the same millisecond count up, so the list stays in order (RFC 9562, section 6.2, and the monotonic rule of the ULID specification).
Random bits and what the IDs are for
- The random bits come from your browser's cryptographic random generator, not from the clock alone.
- Version 4 carries no time and does not sort. Use it when the order does not matter.
- A UUID or ULID is an identifier, not a password or an access key. Do not treat one as a secret.
Worked example: reading the time of a version 7 or ULID
The page makes new random identifiers, so an example has to be an existing one. The first 48 bits of the UUID version 7 in RFC 9562, appendix A.6, are 017f22e279b0. That is 1,645,557,742,000 milliseconds, or 2022-02-22 19:22:22 UTC.
The first ten characters of the ULID 01ARZ3NDEKTSV4RRFFQ69G5FAV, from the ULID specification, are its time: 01ARZ3NDEK is 1,469,922,850,259 milliseconds, or 2016-07-30 23:54:10.259 UTC.
| Identifier | Time part | Time (UTC) |
|---|---|---|
| 017f22e2-79b0-7cc3-98c4-dc0c0c07398f (UUID version 7) | 1,645,557,742,000 ms | 2022-02-22 19:22:22 |
| 01ARZ3NDEKTSV4RRFFQ69G5FAV (ULID) | 1,469,922,850,259 ms | 2016-07-30 23:54:10.259 |
Frequently asked questions
What is the difference between UUID v4, v7 and ULID?
Version 4 is random and carries no time. Version 7 is a UUID that starts with the Unix time in milliseconds, and a ULID is a 26-character text built on the same idea. Use version 7 or ULID when the order of creation matters.
Can two generated identifiers be the same?
The random space of version 4 is 2 to the power 122, so two equal identifiers are practically impossible. Within one batch, version 7 and ULID identifiers made in the same millisecond never repeat, because their counter counts up.
Are these identifiers safe to use as passwords or access keys?
No. An identifier is not designed to be secret, and a version 7 or ULID shows the time it was made. Use a token generator built for secrets.
Why does the time show when I decode a version 7 or ULID?
Both store the creation time in their first 48 bits, as milliseconds since 1970. Anyone who sees the identifier can read that time, so do not put private information in it.
Does the page store or send the identifiers?
No. They are made in your browser and are not stored, uploaded or logged.
Sources
- RFC 9562: Universally Unique IDentifiers (UUID), sections 5.4, 5.7 and 6.2 (IETF)
- ULID specification (GitHub, ulid/spec)
- Crockford base32 encoding (Douglas Crockford)
Figures and text last checked on Tuesday, November 10, 2026.