UUID Version
UUID v4 Generator
Create version-4 UUIDs — the most common kind of universally unique identifier. Every value is built from 122 random bits produced locally by your browser's secure random generator.
Random v4 (RFC 4122)122 secure random bitsNothing leaves your browser
Generated locally with the Web Crypto API — nothing leaves your browser.
What Is UUID v4 Generator?
- A UUID v4 is a 128-bit identifier where 122 of the bits are randomly generated. That randomness makes collisions effectively impossible at any realistic scale, which is why v4 is the default choice for unique IDs across databases, APIs and distributed systems.
- The version digit (
4) and the RFC 4122 variant bits are fixed; the remaining 122 bits are taken from a cryptographically secure random source, so two independently generated v4 UUIDs will essentially never match.
How to generate
- Set how many UUIDs you need (1–1000).
- Toggle the formatting options: uppercase, hyphens and braces.
- Press Generate. Copy a single value, copy them all, or export the batch as .txt / .csv.
Use Cases
- Primary keys for databases that accept client-generated IDs.
- Request and transaction IDs that must be unique across services.
- Test fixtures and placeholder data during development.
- File and object names that must never collide.
How UUID v4 Generator Compares
| UUID v4 | Fully random; simplest, most popular |
| UUID v7 | Time-ordered; better for database indexes |
| UUID v3/v5 | Name-based; deterministic from a name |
Code Examples
JavaScript
const { v4 } = require('uuid');
const id = v4(); // '9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d'Python
import uuid
id = uuid.uuid4()Frequently Asked Questions
Why is UUID v4 the most popular version?
Because it needs no central authority and no input beyond randomness. v1 reveals a timestamp and node, v3/v5 need a name, but v4 is simply random — the easiest way to get a guaranteed-unique value anywhere.
Can a UUID v4 ever repeat?
In practice, no. With 122 random bits the chance of an accidental collision only reaches 50% after about 2.7 × 1018 generated values, far beyond any real workload.
Should I store UUIDs with or without hyphens?
Storage usually keeps the canonical hyphenated form (32 hex digits in 8-4-4-4-12). Drop hyphens only if you need a compact 32-character string, but keep the value lowercase or uppercase consistently.