UUID Generator
A UUID is a 128-bit identifier written as 32 hexadecimal digits, normally grouped by hyphens into 36 characters. It is designed so that separate systems can create ids independently, with no central counter, and still not collide. That is why UUIDs turn up as database keys, request and correlation ids, and ids in test data.
This generator produces version 4 UUIDs, the random kind. Choose how many you want (1, 5, 10, 25 or 50) and a format, and copy the whole batch with one click.
Runs in your browser. UUID Generator processes your input on your own device. Nothing you enter or upload is sent to a server.
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(opens in a new tab)How to use the UUID Generator
- Choose how many UUIDs you need: 1, 5, 10, 25 or 50.
- Choose a format: standard, uppercase, no dashes or with braces.
- Select Generate UUIDs. Each one appears on its own line.
- Select Copy All, or generate again for a fresh batch.
Output formats
The format changes only how the same kind of value is written. The examples below show one UUID in each style.
| Format | Looks like | Typical use |
|---|---|---|
| Standard | 9f1c2d3e-4a5b-4c6d-8e7f-0a1b2c3d4e5f | Databases, APIs and most libraries. |
| UPPERCASE | 9F1C2D3E-4A5B-4C6D-8E7F-0A1B2C3D4E5F | Places where an existing convention writes identifiers in capitals. |
| No Dashes | 9f1c2d3e4a5b4c6d8e7f0a1b2c3d4e5f | A compact 32-character form for file names or fields that do not allow hyphens. |
| With Braces | {9f1c2d3e-4a5b-4c6d-8e7f-0a1b2c3d4e5f} | The brace-wrapped GUID style common in Windows contexts. |
How to recognise a version 4 UUID
Every v4 UUID follows the pattern xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. The 4 at the start of the third group is the version, and y, the first digit of the fourth group, is always 8, 9, a or b. The other 122 bits are random. If an id from somewhere else has a different digit in that third-group position, it is a different UUID version.
The random bits come from your browser's crypto.getRandomValues() source rather than Math.random(). The values are generated on your device and are not sent anywhere.
A UUID identifies something. It is not designed to be a password. For one of those, use the Password Generator.
Things worth knowing
- Only version 4 is generated. There are no time-based (v1), time-ordered (v6, v7) or name-based (v3, v5) UUIDs.
- A batch is limited to 50. Generate again for more.
- It creates UUIDs; it does not validate or convert ones you already have.
Frequently asked questions
What is a version 4 UUID?
One whose bits are random apart from the small fixed portion that marks the version and variant. Other versions derive their value from a timestamp, a MAC address or a hash of a name instead.
Is a UUID the same as a GUID?
In practice, yes. GUID is Microsoft's name for the same 128-bit identifier. If a Windows tool expects the braces or capitals it usually writes, choose the With Braces or UPPERCASE format.
Can two UUIDs ever collide?
In principle yes, but the space is 122 random bits, so the probability is negligible for any realistic number of ids. They are treated as unique in practice.
Are UUIDs a good primary key?
They are excellent when ids must be generated by clients or by several services at once. The trade-off is that random keys scatter writes across a B-tree index and take more space than an integer, which is why some teams prefer time-ordered schemes such as UUID version 7 for large tables. This tool does not generate version 7.
Are the UUIDs stored or sent anywhere?
No. They are generated in your browser and disappear when you leave the page.