A UUID (Universally Unique Identifier) is a 128-bit value that lets you create unique IDs with an extremely low chance of collision, all without any central coordination. They are widely used wherever you need a value that must not clash — database primary keys, transaction IDs, file names, identifiers in distributed systems, and more. The key advantage is that multiple servers can issue IDs at the same time, with no coordination between them, and still avoid collisions. This tool generates the most common version 4 (fully random) UUIDs, producing as many as you want at once.
A version 4 UUID is a 36-character string in the 8-4-4-4-12 shape (for example, 550e8400-e29b-41d4-a716-446655440000), where the first digit of the third group is always 4 to indicate the version. Because 122 bits are random, the generation space is effectively limitless, so at any realistic scale the same value will almost never appear twice.
Generation uses crypto.randomUUID, built into the browser. It draws on a cryptographically secure source of randomness, making it far less predictable than a simple Math.random-based generator. Every UUID is created in your browser with no server communication, and the tool offers uppercase formatting, a hyphen-removal option, and the ability to copy the entire list at once.
How to Use
- 1
Enter a count
Set how many UUIDs to generate at once, anywhere from 1 to 100.
- 2
Choose a format
If needed, turn on the 'Uppercase' and 'Remove hyphens' options to match the notation you want.
- 3
Generate
Press the 'Generate' button and the chosen number of fresh UUIDs is built into a list.
- 4
Copy
Use each item's copy button to grab them one by one, or 'Copy all' to take every UUID separated by line breaks.
When It's Useful
Generate database primary keys
Using UUIDs as primary keys instead of auto-increment integers lets multiple servers or clients mint IDs ahead of time without collisions.
Populate test and seed data
Create dozens of UUIDs at once to use as identifiers in mock data, fixtures, and API test cases.
Correlation IDs and request tracing
Issue random UUIDs as trace IDs or idempotency keys to stitch logs together across a distributed system.
Collision-free file and resource names
Attach a UUID to uploaded files or temporary resources to prevent overwrites during concurrent work.
Tips
- When using them as database keys, the hyphen-free 32-character form saves a little storage space.
- UUID v4 is random-based, so sorting cannot reveal the order of creation. If you need chronological ordering, consider UUID v7 or ULID.
- The collision probability is astronomically low, but not zero. If absolute uniqueness is essential, pair it with a unique constraint in your database.
- Letter case can make the same UUID look different, so it is safest to standardize on one notation when comparing values.
- Using random UUIDs as a clustered index key scatters insert positions and can hurt performance. If you do frequent bulk inserts, consider a time-ordered type like v7.
- crypto.randomUUID works in a secure context (HTTPS). This tool also includes a fallback for older environments that do not support it.
FAQ
Which version of UUID is this?
It generates version 4 (fully random) UUIDs. They use the 36-character form (with hyphens), and the third group starts with 4.
Are they really unique?
The collision probability of a version 4 UUID is low enough to be effectively negligible. Still, it is not theoretically zero, so for critical systems we recommend also using a database unique constraint.
Are the generated values sent to a server?
No. Every UUID is created with the browser's crypto.randomUUID and is never transmitted anywhere.
How many can I make at once?
This tool can generate up to 100 per run. If you need more, press the button again to generate additional ones.
Is it the same UUID after removing hyphens?
Yes. Hyphens are just separators for readability, so removing them leaves the identifier unchanged. Just keep the format consistent when storing and comparing.
Is crypto.randomUUID a sufficiently secure random source?
Yes. It uses a cryptographically secure random number generator, so it is safer than a Math.random-based generator that is vulnerable to guessing attacks.
What is the difference between UUID v4 and v7?
v4 is fully random and has no ordering, while v7 embeds a timestamp at the front so values sort by creation time. v7 is advantageous when database insert performance matters, but this tool generates the most widely used v4.
Can I tell the creation order or time from a UUID?
Not with version 4. Everything is random, so sorting cannot reconstruct the order they were made. If you need timing information, use UUID v7 or ULID.