UUID Generator
Generate random version-4 UUIDs — one or up to 100 at a time — using your browser's cryptographic randomness. Copy them individually or all at once.
What is a UUID v4?
A UUID (universally unique identifier) is a 128-bit number written as 32 hexadecimal digits in five hyphen-separated groups, like 550e8400-e29b-41d4-a716-446655440000. Version 4 UUIDs are built from random data: 122 of the 128 bits are random, and 6 bits are fixed to mark the version (the digit 4 in the third group) and the variant (8, 9, a, or b at the start of the fourth group).
Collisions are astronomically unlikely. There are about 5.3 × 10^36 possible v4 UUIDs, so you could generate a billion per second for roughly 85 years before reaching even a 50% chance of one duplicate — which is why UUIDs are used as database keys, request IDs, and file names without any central coordination.
This tool uses the Web Crypto API (crypto.randomUUID, with a crypto.getRandomValues fallback), so every UUID comes from a cryptographically secure random number generator and is created entirely in your browser.
Frequently Asked Questions
- What is a UUID v4?
- A UUID (universally unique identifier) is a 128-bit identifier written as 32 hexadecimal digits in five hyphen-separated groups, like 550e8400-e29b-41d4-a716-446655440000. Version 4 UUIDs are generated from random data — 122 of the 128 bits are random, while 6 bits are fixed to mark the version and variant.
- Can two generated UUIDs ever collide?
- In theory yes, in practice no. With 122 random bits there are about 5.3 undecillion (5.3 × 10^36) possible v4 UUIDs. You would need to generate roughly a billion UUIDs every second for about 85 years to reach even a 50% chance of a single collision.
- Is the randomness cryptographically secure?
- Yes. UUIDs are generated with the browser's Web Crypto API (crypto.randomUUID, falling back to crypto.getRandomValues), which uses a cryptographically secure random number generator — not the predictable Math.random.
- Are the UUIDs generated on a server?
- No. Everything runs locally in your browser, so the UUIDs never travel over the network and cannot be logged by anyone. Refreshing the page produces a completely new, unrelated set.
- What are the uppercase and no-hyphens options for?
- Some systems store or compare UUIDs in uppercase, and some (like certain databases and APIs) expect the 32-character form without hyphens. The options reformat the same underlying value — case and hyphens don't change a UUID's identity per RFC 4122, which treats them as equivalent.