What is a UUID used for?

UUIDs uniquely identify things like database records, distributed-system entities, and session tokens without needing a central authority to hand out sequential IDs.

Are these UUIDs truly random?

Yes. Version 4 UUIDs are generated from a cryptographically secure random number generator via the browser's native crypto.randomUUID() — 122 of the 128 bits are random.

Are there other types of UUID?

Yes — version 1 is timestamp-based and version 5 is namespace-based (deterministic). This tool only generates version 4, the most common general-purpose type.

UUID Generator — Free Version 4 UUID Tool

UUID Generator

Generate a random version 4 UUID, entirely in your browser.

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What This Tool Does

A UUID (Universally Unique Identifier) is a 128-bit value used to identify something — a database record, a distributed-system entity, a session token — without needing a central authority to hand out sequential IDs. This tool generates a fresh, random version 4 UUID on demand, entirely in your browser.

How to Use It

A UUID is generated automatically as soon as the page loads. Click Generate Another for a new one, or use the Copy button to grab the current value directly.

The Formula

This uses the browser's native crypto.randomUUID(), which generates a version 4 UUID directly from a cryptographically secure random number generator. Version 4 UUIDs are almost entirely random — 122 of the 128 bits are random, with a handful of fixed bits marking the version and variant — which makes collisions astronomically unlikely without needing any coordination between generators. UUIDs also come in other versions for different purposes: version 1 is timestamp-and-node-based (encodes when and, historically, on what device it was generated), and version 5 is namespace-based (deterministically derived from a namespace and a name, so the same inputs always produce the same UUID) — this tool only generates version 4, the most common general-purpose type, and doesn't implement the others.

A Worked Example

A typical output looks like f47ac10b-58cc-4372-a567-0e02b2c3d479— 32 hexadecimal characters split into five groups by hyphens. The third group always starts with "4" (the version marker) and the fourth group always starts with 8, 9, a, or b (the variant marker); every other character is effectively random. This structure is exactly what a database primary key, an API request ID, or a session token commonly uses when IDs need to be generated independently across many machines without ever colliding.

FAQ

What is a UUID used for?: UUIDs uniquely identify things like database records, distributed-system entities, and session tokens without needing a central authority to hand out sequential IDs.
Are these UUIDs truly random?: Yes. Version 4 UUIDs are generated from a cryptographically secure random number generator via the browser's native crypto.randomUUID() — 122 of the 128 bits are random.
Are there other types of UUID?: Yes — version 1 is timestamp-based and version 5 is namespace-based (deterministic). This tool only generates version 4, the most common general-purpose type.