UUID Generator
Create cryptographically random identifiers — UUID v4, sortable ULIDs, or compact Nano IDs — one at a time or hundreds at once.
How it works
UUID v4 is 122 random bits in a fixed layout. The randomness comes from your browser's cryptographic generator, not Math.random, so the values are suitable for identifiers that must not be guessable.
ULID and Nano ID solve different problems. A ULID starts with a millisecond timestamp, so ids sort chronologically and database indexes stay compact — random UUIDs scatter writes across an index and fragment it. A Nano ID is simply shorter for the same collision resistance, with no dashes to escape in a URL.
The formula
UUID v4
122 random bits, with version 4 and the variant bits fixed
ULID
48-bit timestamp + 80 random bits, Crockford base32
Collision odds
≈ 50% after 2.71 × 10¹⁸ UUIDs — effectively never in practice
Worked examples
| Scenario | Working | Result |
|---|---|---|
| UUID v4 | 8-4-4-4-12 hex | f47ac10b-58cc-4372-a567-0e02b2c3d479 |
| ULID | Timestamp first | Sorts by creation time |
| Nano ID | 21 URL-safe characters | Shorter, no dashes |
When you'd use it
- Seeding test data with realistic identifiers
- Creating a primary key before a record is saved
- Generating correlation ids for tracing requests
- Filling a config that needs a unique instance id
Common questions
Are these safe to use as database keys?
Yes, though UUID v4's randomness scatters inserts across the index, which hurts write performance at scale. If that matters, use a ULID — the timestamp prefix keeps new rows adjacent.
Could two of these ever collide?
In practice, no. You would need to generate billions per second for decades before a collision became likely. That holds only because the randomness is cryptographic, which it is here.
Are the generated ids sent anywhere?
No. They are created in your browser and never transmitted, so they are safe to use as secrets or keys.