How to Generate UUIDs Online (Real Cryptographic Randomness)

Test data that needs unique IDs, a placeholder identifier while prototyping before a real ID system exists, a batch of unique keys for a script — a UUID generator is a small, frequently-needed tool, and the quality of its randomness matters more than it might seem for a "just generate an ID" task.

What a UUID v4 Actually Is

A UUID (universally unique identifier) is a 128-bit value, conventionally written as 32 hex characters split into five groups: 550e8400-e29b-41d4-a716-446655440000. Version 4 — the most common type, and what QR Ivify's UUID Generator produces — is randomly generated rather than derived from a timestamp or namespace, with a couple of fixed bits marking it as version 4. With 122 bits of actual randomness, the odds of two independently generated v4 UUIDs ever colliding are astronomically small — small enough that "unique" is a safe assumption in practice.

Why the Random Source Matters

That "astronomically small collision odds" guarantee only holds if the randomness is actually good. crypto.randomUUID() — the modern, native browser method this tool uses first — is built on the same cryptographically secure random number generator used for real security purposes, not Math.random(), which is a faster but weaker pseudo-random generator whose output can, in some engines, be inferred from enough samples. For an ID that just needs to be unique, that difference is mostly academic — but it costs nothing to use the stronger source, so there's no reason not to.

Step by Step

1. Open the UUID Generator.
2. Choose how many UUIDs to generate — 1, 5, 10, 50, or 100.
3. Click "Generate."
4. Copy or download the list.

What Happens on an Older Browser

crypto.randomUUID() is available in every current browser, but for the rare older one without it, this tool falls back to building a valid v4 UUID by hand — using crypto.getRandomValues(), the same secure random source randomUUID() itself is built on, just assembled manually into the correct UUID v4 byte layout. The unpredictability guarantee doesn't depend on that one specific function existing.

Frequently Asked Questions

Are these truly random, or predictable? They're generated using the Web Crypto API (crypto.randomUUID(), or a manual fallback built on the same cryptographically secure crypto.getRandomValues()), never Math.random().

What UUID version does this generate? Version 4 — randomly generated, the most common type for general-purpose unique identifiers.

Does this upload anything to a server? No. Every UUID is generated entirely in your browser.

What if my browser doesn't support crypto.randomUUID()? A fallback generates a valid v4 UUID by hand from the same secure random source, so the guarantee of unpredictability doesn't depend on that specific function existing.

Try It

Need unique IDs for test data, a prototype, or a script? QR Ivify's free UUID Generator uses real cryptographic randomness, up to 100 at a time. Need a random string with more control over character types instead? See the Password Generator.