UUID generator
The UUID generator creates any number of random version 4 UUIDs — 128-bit values written as 36 characters in the form xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. They work as unique keys in databases, file names, object identifiers in APIs, or message IDs. Everything is generated by your browser's cryptographic generator right on your device — no data is ever sent anywhere and no sign-up is needed.
How the UUID generator works
A UUID (Universally Unique Identifier) is a 128-bit number that serves as a globally unique identifier without needing any central registry. It is written as 32 hexadecimal digits split by hyphens into five groups of 8-4-4-4-12, for example f47ac10b-58cc-4372-a567-0e02b2c3d479. This tool generates the version 4 variant, which is based purely on randomness.
The randomness does not come from the ordinary Math.random() function but from the built-in cryptographic generator of the browser via crypto.randomUUID(). It fills the value with random bits and then sets two fixed positions prescribed by the standard: the version digit (always 4 at the start of the third group) and the variant (the first character of the fourth group is always 8, 9, a or b). The remaining 122 bits are random.
Those 122 random bits are exactly what makes a UUID practically unique: a collision — generating two identical UUIDs — is so improbable that it is never accounted for in normal operation. That is why identifiers can be generated independently on many machines without them ever having to coordinate.
How to use the UUID generator
- In the Count field, enter how many UUIDs you want at once (1 to 100).
- Click Generate. The list is printed instantly into the text area, each UUID on its own line.
- Use the Copy button to copy the whole list to the clipboard and paste it into your code, a spreadsheet, or a database.
- Need a different set? Click Generate again — you get new random values every time.
Example output for a count of 3:
| # | UUID v4 |
|---|---|
| 1 | 3d6f0e7a-1b2c-4d9e-8f01-2a3b4c5d6e7f |
| 2 | b1e2c3d4-5f6a-4b8c-9d0e-1f2a3b4c5d6e |
| 3 | 7a8b9c0d-1e2f-4a3b-b4c5-6d7e8f901a2b |
Notice that the third group of each UUID starts with the digit 4 (version) and the fourth group starts with a character from the range 8–b (variant) — that is the signature of a UUID v4.
What the UUID generator is good for
UUIDs are used mainly by developers and system administrators wherever they need a unique identifier that each party can create on its own:
- Primary keys in databases — unlike a numeric sequence 1, 2, 3, a UUID can be generated on the client before saving and does not reveal the number of records.
- File names and uploaded attachments — prevents conflicts when multiple users upload a file with the same name.
- Identifiers in APIs and distributed systems — request IDs, transaction IDs, message keys in queues, correlation IDs for logging.
- Idempotency keys — so a resent request is not processed twice.
Because generation happens entirely in your browser and a v4 UUID contains no information about your device, the time, or a MAC address (as the older version 1 used to), no trail leading back to you is created. For sensitive use, keep in mind that a UUID is an identifier, not a security token — it is not secret and should never serve as a password. For passwords, use a dedicated generator.
FAQ
What does "v4" mean in a UUID?
It refers to version 4, a UUID made up entirely of random bits (apart from the fixed version and variant digits). Other versions exist — e.g. v1 based on time and MAC address, or v7 sortable by time — but v4 is the most common for general-purpose unique identifiers.
Are the generated UUIDs truly unique?
They are not mathematically guaranteed to be unique, but in practice they are. A v4 UUID has 122 random bits, so the probability of a collision is negligible even across billions of generated values. Normal operations do not account for duplicates.
Does the tool send my data to a server?
No. UUIDs are generated locally in your browser using crypto.randomUUID(). Nothing is uploaded, stored, or sent — the tool even works offline once the page has loaded.
Can I use a UUID as a password or security token?
Not recommended. A UUID is an identifier meant to distinguish objects, not to keep something secret. It is random, but its format is predictable and public. For passwords and tokens, use a password generator with sufficient entropy.
How many UUIDs can I generate at once?
With this tool, 1 to 100 at a time. For larger batches, click Generate repeatedly — each click gives you a completely new set of random values.
Are UUIDs case-sensitive?
The standard recommends lowercase output, but for comparison a UUID is treated as equal regardless of letter case. The value <code>F47AC10B…</code> is identical to <code>f47ac10b…</code>. This tool generates lowercase.
Why does the third group always start with the digit 4?
It is the signature of version 4. The standard reserves one position for the version number, so for v4 it is always 4. Similarly, the first character of the fourth group (8, 9, a or b) marks the variant.
Can I generate the same UUID twice by clicking Generate?
In theory yes, in practice no. Each click draws new random values, and the chance of hitting two identical UUIDs is so tiny it can be ignored in practice.
Sources & standards
📅 Last updated: 16 July 2026