UUID Generator

Generate cryptographically random UUID v4 identifiers, one or many at a time.

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How it works

Each UUID is produced by the browser's built-in crypto.randomUUID() function, which is required by the WHATWG specification to use the same cryptographically secure random source as crypto.getRandomValues(). Output is always RFC 4122 version 4 — 122 random bits with the version and variant bits fixed. Probability of collision is astronomical: about 1 in 2.71 quintillion for a single comparison. Generation is instant; nothing leaves your device.

Common use cases

  • Seeding a database with stable, conflict-free primary keys during development.
  • Generating correlation IDs to thread through log lines.
  • Producing unique React keys for prototypes that lack natural identifiers.

Frequently asked questions

Is this UUID v4 or another variant?

V4 — random. crypto.randomUUID() is specified to return v4 only. For v1 (timestamp), v5 (namespace SHA-1) etc you need a library.

How random is it really?

Cryptographically secure. The same source backs HTTPS session keys, password generators and the Web Crypto API.

Can I generate hundreds at a time?

Yes — set the count input. Browser stays responsive up to several thousand without issue.

Are these stored anywhere?

No. They are generated locally and only exist in your browser tab.