UUID Generator

What is UUID Generator?

A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit identifier that can be generated on any machine without coordination and be effectively guaranteed unique. UUIDs are the go-to primary key for distributed systems, event ids, upload names, and anything that needs a unique id without a central sequence.

How to generate UUIDs online

1. 1Pick the UUID version: v4 (random) or v7 (time-ordered, RFC 9562).
2. 2Choose how many UUIDs to generate (1 to 1000).
3. 3Click Generate — the list appears instantly.
4. 4Click Copy on any row to grab a single UUID, or Copy All to copy the whole list.

Use Cases

Code Examples

// Modern browsers & Node 19+
const id = crypto.randomUUID();

// npm i uuid
import { v7 as uuidv7 } from "uuid";
const id = uuidv7();

import uuid
print(uuid.uuid4())            # random
# uuid7 not in stdlib yet; use uuid7 package

import "github.com/google/uuid"

id := uuid.New()               // v4
// For v7: github.com/gofrs/uuid/v5

-- PostgreSQL
SELECT gen_random_uuid();      -- v4
-- MySQL 8+
SELECT UUID();

Key Concepts

UUID v4

Fully random 128-bit id (122 bits of entropy). Collision probability is essentially zero even at billions of IDs.

UUID v7 (RFC 9562)

First 48 bits are a Unix millisecond timestamp, rest is random. Sortable by creation time — ideal as a database primary key.

ULID

A UUID-compatible 128-bit id with millisecond timestamp + randomness, but encoded in Crockford Base32 (26 chars, no dashes). UUID v7 largely obsoletes ULID.

NanoID

Shorter (21 chars) alternative for URLs, using a custom alphabet. Not a UUID and not sortable, but URL-friendly.

Tips & Best Practices

• ▸For new databases: prefer UUID v7 over v4. It's monotonic, indexes better, and reveals no more information than v4 does (still random after the timestamp).
• ▸Store UUIDs as `uuid` type (Postgres) or `BINARY(16)` (MySQL). Storing as `VARCHAR(36)` doubles storage and slows every index scan.
• ▸Never expose sequential integer IDs in URLs if enumeration is a risk. UUIDs are effectively unguessable.
• ▸For very high-write workloads, UUID v7 also helps avoid the 'random insert' write-amplification problem that plagues v4 primary keys.