How to generate UUIDs
- Choose v4 for purely random IDs, or v7 for IDs that sort by creation time.
- Enter how many you need — up to 10,000 at once.
- Pick a format and press Generate. Copy them all or download them as a text file.
What is a UUID?
A UUID (Universally Unique Identifier), also called a GUID in the Microsoft world, is a 128-bit identifier written as 32 hexadecimal digits in five groups: 8-4-4-4-12, for example 3f2b8c1e-9d4a-4b7e-8f21-6c5d0a9e7b13. UUIDs let different systems create IDs independently — without asking a central database for the next number — with practically zero chance of collisions.
v4 vs. v7
| UUID v4 | UUID v7 | |
|---|---|---|
| Built from | 122 random bits | 48-bit Unix timestamp in milliseconds + 74 random bits |
| Sort order | Random | Roughly chronological |
| Database index performance | Can fragment B-tree indexes | Inserts stay ordered, much like auto-increment |
| Reveals creation time | No | Yes (to the millisecond) |
| Standard | RFC 4122 / RFC 9562 | RFC 9562 (2024) |
Use v7 for database primary keys and event IDs where ordering helps. Use v4 when the ID must not reveal when it was created, such as public tokens.
How unique are they?
A v4 UUID has 2122 possible values — about 5.3 × 1036. You would need to generate around a billion UUIDs every second for roughly 85 years before having a 50% chance of a single duplicate. The real-world risk comes from poor random number generators, which is why this tool uses crypto.getRandomValues(), the browser’s cryptographically secure source.
UUIDs in code
- JavaScript:
crypto.randomUUID()(v4) - Python:
uuid.uuid4() - PostgreSQL:
gen_random_uuid()(v4); version 18 addsuuidv7() - MySQL:
UUID()returns v1
Frequently asked questions
Are UUID and GUID the same?
Yes. GUID is Microsoft’s name for the same 128-bit identifier. Microsoft tools often show them in uppercase inside braces.
Can two generated UUIDs be the same?
In theory yes, in practice no. With properly random generation the probability is so small it can be ignored.
Should I use UUIDs as database keys?
They work well, especially v7, which keeps index inserts ordered. They use more storage (16 bytes) than integer IDs.
Are these UUIDs generated on a server?
No. They are generated in your browser with cryptographically secure randomness.