Do UUIDs really never collide?

For v4, even generating one billion per second would take about 85 years to reach a 50% collision probability. For typical applications, collisions are not a concern.

Are secure random numbers used?

This page uses the browser's crypto.getRandomValues() (a cryptographically secure random number generator). Math.random() is never used.

Are generated UUIDs sent to any server?

No. All generation and processing happen entirely inside your browser. No data is transmitted externally.

UUID Generator - v4 · v7 · NIL

Q: Why no v1, v3, or v5?

v1 leaks the MAC address and is discouraged; v3 and v5 require a namespace and are not suited for general-purpose generators. We provide only the most practical v4, v7, and NIL.

UUID Version

v4 (random) v7 (time-based) NIL

Count Format

Standard No hyphens Braces {…} Base64 (URL-safe)

Case

Lowercase Uppercase

Separator

Newline Comma JSON array SQL INSERT

Wrap each UUID in quotes

Result

Pick options above and press Generate.

UUID Inspector

Paste a UUID to see its version, variant, and creation time (v7).

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier defined by RFC 4122 / RFC 9562. It can be generated independently with a near-zero collision probability, making it ideal for database primary keys, distributed systems, and file identifiers.

Versions at a glance

v4 (random) — 122 random bits. The most common variant; unpredictable. Collision probability is effectively zero.
v7 (time-based, recommended) — The first 48 bits are a Unix millisecond timestamp, so values sort in time order. Database-index friendly and recommended over v4 in modern systems.
NIL — All bits set to zero (00000000-0000-0000-0000-000000000000). Used to represent an "empty" UUID.

Why prefer v7?

UUID v4 is fully random and tends to fragment B-tree indexes when inserted into databases. v7 is monotonically increasing in time, so new rows append to the end of the index — better INSERT performance, and you can recover the creation time directly from the UUID.

FAQ

Will UUIDs ever collide?

Even at 1 billion v4 UUIDs per second, you'd need around 85 years to reach a 50% collision probability. For typical applications, collisions are not a concern.

Is the randomness secure?

This page uses the browser's crypto.getRandomValues() (cryptographically secure RNG). It does not use Math.random().

Are generated UUIDs sent to a server?

No. Everything happens in your browser. No data leaves your device.

Why no v1, v3, or v5?

v1 leaks MAC addresses and is discouraged; v3/v5 require namespaces and don't fit a general-purpose generator. We provide the most practical versions: v4, v7, and NIL.