Free UUID Generator (v4 and v1)
Generate universally unique identifiers using your browser's cryptographic random source. Bulk generation supported.
Why distributed systems rely on UUIDs
A UUID is 128 bits, conventionally displayed as 32 hexadecimal digits split into five groups by hyphens (8-4-4-4-12), like f47ac10b-58cc-4372-a567-0e02b2c3d479. The reason UUIDs exist at all comes down to coordination: a traditional auto-incrementing database ID requires a single authority (the database) handing out the next number in sequence, which falls apart the moment you have multiple servers, offline clients, or merging databases that each need to mint IDs independently without colliding. A v4 UUID needs no coordination at all — any machine, anywhere, can generate one from local randomness and it will practically never collide with an ID generated anywhere else.
That's also why v4 (random) and v1 (timestamp-based) serve different purposes. v1 UUIDs sort roughly by creation time, which some database engines can index more efficiently than a fully random key, but they leak the exact moment the identifier was created — which v4 deliberately does not.
Frequently Asked Questions
What is the difference between UUID v4 and v1?
v4 UUIDs are generated from 122 bits of random data and are the standard choice for most applications. v1 UUIDs embed the current timestamp, so they sort roughly by creation time — useful for database keys where insertion order matters — but they reveal when they were created.
Are these UUIDs really unique?
Practically, yes. The probability of two random v4 UUIDs colliding is so small (about 1 in 2¹²²) that you would need to generate billions of UUIDs per second for decades before a duplicate becomes likely.
Is it safe to use these in production?
Yes. v4 UUIDs are generated with the Web Crypto API (crypto.randomUUID / crypto.getRandomValues), which is cryptographically secure. The v1 node identifier is randomized per the RFC 4122 privacy recommendation rather than using your real MAC address.
Why use a UUID instead of an auto-incrementing integer for a database key?
An auto-incrementing integer needs one authority handing out the next number, which doesn't scale cleanly across multiple servers, offline-first apps, or merged databases. Any machine can generate a UUID independently with no coordination and effectively no collision risk, which is exactly what distributed systems need.
Do the hyphens in a UUID mean anything?
They're purely a readability convention marking the standard 8-4-4-4-12 hex-digit grouping — they carry no data of their own, which is why this tool offers a "No hyphens" option that produces an equally valid, functionally identical UUID.
Are the UUIDs generated on a server?
No. All generation happens locally in your browser, so the identifiers are never transmitted or logged anywhere.