UUID Generator

Generate random UUID v4 values for use in databases, APIs, or testing.

How many UUIDs to generate (1–10).

UUID

8f9fa188-6d51-4527-aa52-24056a48728a

Additional UUIDsNone
Versionv4 (random)
Formula Formula Assumptions 2 Example Example Sources 2 Last updated Mar 11, 2026
Inputs stay in the browser unless a future feature explicitly tells you otherwise. Use this as an estimate and validate important decisions with a qualified professional.

How to use this UUID generator

  1. Set the number of UUIDs

    Enter 1–10 in the Number of UUIDs field to specify how many identifiers to generate.

  2. Generate

    The calculator produces random UUID v4 values using the browser's cryptographic random source.

  3. Copy the result

    Copy the generated UUID(s) for use in databases, API payloads, or test fixtures.

Methodology

How this UUID generator works

This tool generates version 4 UUIDs using browser randomness. UUID v4 identifiers are 128-bit values with specific bits set to indicate the version (4) and the standard variant used by modern UUID specifications. It uses crypto.randomUUID() when available, otherwise crypto.getRandomValues(); if neither Web Crypto API is available, the tool reports that UUID generation is unsupported instead of emitting weak identifiers.

Formula
UUID v4 = xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx (where y ∈ {8,9,a,b})
v4 Version 4, generated from random or pseudo-random numbers
variant The standard UUID bit pattern used for the variant field (bits 8-9 of byte 8)
Example

Example output: 550e8400-e29b-41d4-a716-446655440000

Generating 1 UUID yields a single value like a1b2c3d4-e5f6-4a7b-8c9d-0e1f2a3b4c5d. The 4 in the third group indicates version 4.

Generating 3 UUIDs returns three distinct values, each with 122 random bits. Use them as primary keys for test records or API resources.

Assumptions
  • ✓ Uses the browser's cryptographic random number API when available.
  • ✓ Does not fall back to Math.random(); if Web Crypto is unavailable, the generator reports that UUID generation is unsupported.
Notes
  • UUID v4 is not sequential and not suitable for use as a sortable primary key in databases that benefit from ordered inserts.
Sources
  1. RFC 9562 — Universally Unique IDentifiers (UUIDs) — UUID v4 format and random-bit structure
  2. MDN — Crypto.randomUUID() — cryptographically secure browser UUID generation

Understanding UUID versions and structure

A UUID (Universally Unique Identifier) is a 128-bit value represented as 32 hexadecimal digits in five groups (8-4-4-4-12). Version 4 UUIDs use random or pseudo-random data for 122 of those bits; the remaining bits encode the version (4) and variant. The probability of a collision is astronomically low — about 1 in 2^122 — so UUIDs are effectively unique without coordination. Other versions exist: v1 uses timestamp and MAC address, v3 and v5 are name-based hashes, and v7 is time-ordered. UUID v4 is the most common choice for distributed systems because it requires no central authority and no shared state to generate.

Developer use cases for UUIDs

Developers use UUIDs as primary keys in databases, correlation IDs in distributed tracing, and unique identifiers in API payloads. Unlike auto-increment integers, UUIDs can be generated client-side or by any service without contacting a central database, which simplifies horizontal scaling and offline-first architectures. They are ideal for merge scenarios where multiple systems create records that are later combined. UUIDs also appear in OAuth state parameters, webhook signatures, and file naming to avoid collisions. When testing, generating UUIDs on demand avoids hardcoding and makes fixtures reproducible. The main trade-off is size (36 characters) and lack of sortability compared to sequential IDs.

Frequently asked questions

Are these UUIDs unique?

For all practical purposes, yes. The chance of generating a duplicate is astronomically small (1 in 2^122).

Can I use these in production?

Yes when the environment provides Web Crypto randomness. If Web Crypto is unavailable, the tool reports UUID generation as unsupported rather than producing security-looking identifiers from weak randomness.

Written by Jan Křenek Founder and lead developer
Reviewed by DigitSum Methodology Review Formula verification and QA
Last updated Mar 11, 2026

Use this as an estimate and validate important decisions with a qualified professional.

Inputs stay in the browser unless a future feature explicitly tells you otherwise.