UUID v4 is a randomly generated 128-bit identifier defined in RFC 4122. The format is 8-4-4-4-12 hexadecimal characters separated by hyphens, like 550e8400-e29b-41d4-a716-446655440000.

Are these UUIDs cryptographically random?

Yes. They use the browser's crypto.randomUUID() API, which is backed by a cryptographically secure random number generator. There are no patterns or predictability.

Can I use these UUIDs in production?

Yes. UUIDs from crypto.randomUUID() are suitable for database primary keys, session IDs, correlation IDs, and any case requiring globally unique identifiers.

Is the UUID sent to a server?

All generation runs in your browser using crypto.randomUUID(). Our servers are not involved at any point.

UUID v4 Generator

Generate a cryptographically random UUID v4 (RFC 4122) in your browser with one click. The result is a 128-bit identifier formatted as 8-4-4-4-12 hexadecimal characters, ready to copy. All generation runs in your browser using crypto.randomUUID().

Generated UUID

VERSION

Runs entirely in your browser

How it works

UUID v4 generation uses the browser's crypto.randomUUID() API, a cryptographically secure random number generator built into every modern browser. No JavaScript library is needed.

Processing runs in your browser

UUIDs are generated entirely in your browser. All processing happens locally in your browser tab. Our servers are not involved at any point. You can inspect this yourselfin your browser's DevTools Network tab.

Technical specification

UUID version 4 (random) is defined in RFC 4122 (IETF, 2005). A UUID v4 contains 122 random bits; the remaining 6 bits encode the version (4) and variant (10xx in bits 64–65). This tool uses the browser's crypto.randomUUID() method (W3C Web Cryptography API), which provides cryptographically strong randomness from the operating system's CSPRNG, equivalent to /dev/urandom on Linux or BCryptGenRandom on Windows.

Standard: RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace
Random bits: 122 bits (of 128 total; 6 bits encode version/variant)
Format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
Collision probability: ~50% at 2.7 × 10¹⁸ UUIDs generated

Related operations

For hashing identifiers into fixed-width values, try the hash generator. To produce strong random secrets, use the password generator. For encoding identifiers for transport, see Base64.

Frequently asked questions

What is a UUID v4?: UUID v4 is a randomly generated 128-bit identifier defined in RFC 4122. The format is 8-4-4-4-12 hexadecimal characters separated by hyphens, like 550e8400-e29b-41d4-a716-446655440000.
Are these UUIDs cryptographically random?: Yes. They use the browser's crypto.randomUUID() API, which is backed by a cryptographically secure random number generator. There are no patterns or predictability.
Can I use these UUIDs in production?: Yes. UUIDs from crypto.randomUUID() are suitable for database primary keys, session IDs, correlation IDs, and any case requiring globally unique identifiers.
Is the UUID sent to a server?: All generation runs in your browser using crypto.randomUUID(). Our servers are not involved at any point.