UUID Generator

Generate random UUIDs (v4) online. Create one or bulk UUIDs instantly. Free UUID/GUID generator.

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What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier that is unique across space and time. UUIDs are used in databases, APIs, and distributed systems to identify resources without a central authority.

Tutorial

How to Generate UUID Online: Quick Reference Guide

Generate UUIDs (v4) online instantly. Learn what UUIDs are, when to use them, and how to generate bulk UUIDs for databases, APIs, and testing.

Video Tutorial

2:15

Video coming soon — full transcript available below

Chapters

Full transcript searchable

0:00

What UUIDs are and when to use them

Welcome to this UUID Generator tutorial. A UUID — Universally Unique Identifier — is a 128-bit number used to uniquely identify objects across systems without a central authority. It looks like: 550e8400-e29b-41d4-a716-446655440000. UUIDs are used as database primary keys (especially in distributed systems), API resource identifiers, session tokens, correlation IDs for logging, and anywhere else you need a unique identifier that doesn't require coordination between systems.

0:30

Generate a single UUID v4

Open the UUID Generator on ToolPilot.dev. Click Generate to create a single UUID v4. UUID v4 is randomly generated — it uses cryptographically secure random numbers to ensure uniqueness. The generated UUID appears in the output field. Click Copy to copy it to your clipboard. Click Generate again for a new UUID. Each click produces a different UUID with vanishingly small probability of collision.

0:55

Batch generate multiple UUIDs

To generate multiple UUIDs at once, enter the count in the batch field (up to 100) and click Generate. The output shows all UUIDs listed one per line, ready to copy as a block. This is useful when seeding a test database, creating a set of API tokens for testing, or pre-generating IDs for a batch of records to insert. The Copy All button copies the entire list.

1:25

UUID v1 vs v4 differences

UUID v1 is time-based — it combines the current timestamp with the machine's MAC address. This means v1 UUIDs are sortable by creation time and include machine identity information. UUID v4 is randomly generated with no timestamp or machine information. For most applications, v4 is preferred because it reveals nothing about when or where it was generated. Use v1 only if you need sortable UUIDs and understand the privacy implications of embedding MAC addresses.

1:50

Use case: database primary keys

UUIDs are popular as database primary keys in distributed systems where multiple nodes insert records simultaneously. Unlike auto-incrementing integers, UUIDs don't require a central sequence generator, so different servers can generate non-conflicting IDs independently. This is essential in microservices architectures, offline-first applications, and multi-region databases. Generate test UUIDs here to use in SQL inserts, migration scripts, or fixture data.

2:05

Wrap-up

The UUID Generator on ToolPilot.dev uses the browser's built-in crypto.randomUUID() function — a cryptographically secure random number generator — ensuring the UUIDs are truly unpredictable. No server is involved, no usage tracking, completely free. Visit ToolPilot.dev for this and 19 other free developer tools.

Transcript covers all 6 chapters (2:15 total).

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Frequently Asked Questions

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 32 hexadecimal digits in the pattern xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. It is designed to be unique across all space and time without requiring a central registry.

What is the difference between UUID v1, v4, and v7?

UUID v1 is time-based and includes the MAC address (privacy concern). UUID v4 is randomly generated — the most commonly used type for database IDs. UUID v7 (newer) is time-ordered like v1 but uses random data like v4, making it better for database indexing.

Are UUIDs truly unique?

UUID v4 generates 2^122 possible values. The probability of a collision is astronomically low — generating 1 billion UUIDs per second for 85 years would give only a 50% chance of one collision. In practice, UUIDs are treated as globally unique.

What is a GUID? Is it the same as a UUID?

GUID (Globally Unique Identifier) is Microsoft's term for UUID. They are the same format and concept. GUIDs in Windows/.NET are UUID v4-compatible.

When should I use a UUID instead of an auto-increment ID?

Use UUIDs when: merging data from multiple databases, exposing IDs in URLs (sequential IDs reveal record count), distributing data across microservices, or generating IDs on the client side before server confirmation.

Can I use UUIDs as primary keys in databases?

Yes, but with caveats. UUID v4 is random, which can cause index fragmentation in B-tree indexes on large tables. UUID v7 (time-ordered) or ULID are better choices for primary keys in high-write databases.

How do I generate a UUID in JavaScript?

In modern browsers and Node.js: crypto.randomUUID() generates a UUID v4. For older environments, use the 'uuid' npm package: import { v4 as uuidv4 } from 'uuid'; uuidv4();

How do I generate a UUID in Python?

Use the built-in uuid module: import uuid; str(uuid.uuid4()) generates a UUID v4 string like '550e8400-e29b-41d4-a716-446655440000'.

Can I generate multiple UUIDs at once?

Yes. The UUID Generator on Toolpilot lets you generate a bulk list of UUIDs in a single click. Specify the count and all UUIDs are generated instantly in your browser.

Code Examples

Ready-to-use implementations in popular programming languages. Copy, paste, and run.

Generate UUID in JavaScript

// Generate UUID v4 (random) using Web Crypto API
const uuid = crypto.randomUUID();
console.log(uuid); // e.g. 550e8400-e29b-41d4-a716-446655440000

// Validate UUID format
function isValidUUID(str) {
  const pattern = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
  return pattern.test(str);
}

console.log(isValidUUID(uuid)); // true

Generate UUID in Python

import uuid

# Generate UUID v4 (random)
id_v4 = uuid.uuid4()
print(id_v4)  # e.g. 550e8400-e29b-41d4-a716-446655440000

# Generate UUID v1 (timestamp-based)
id_v1 = uuid.uuid1()
print(id_v1)

# Generate UUID v5 (namespace + name)
id_v5 = uuid.uuid5(uuid.NAMESPACE_DNS, 'example.com')
print(id_v5)  # always the same for same input

Generate UUID in Go

package main

import (
	"crypto/rand"
	"fmt"
)

func newUUID() string {
	b := make([]byte, 16)
	rand.Read(b)
	b[6] = (b[6] & 0x0f) | 0x40 // Version 4
	b[8] = (b[8] & 0x3f) | 0x80 // Variant
	return fmt.Sprintf("%x-%x-%x-%x-%x",
		b[0:4], b[4:6], b[6:8], b[8:10], b[10:])
}

func main() {
	fmt.Println(newUUID())
}

Generate UUID in Bash

# Generate UUID v4 on Linux
cat /proc/sys/kernel/random/uuid

# Generate UUID v4 on macOS
uuidgen | tr '[:upper:]' '[:lower:]'

# Generate UUID with Python one-liner
python3 -c 'import uuid; print(uuid.uuid4())'

Related Workflow Guides

🆔 Design ID Systems: Generate UUIDs → Hash → Format as JSON → 🏗️ Rapid Prototyping: Lorem Ipsum → UUIDs → Mock JSON → ⚙️ Generate Unique Test IDs for Integration Tests in GitHub Actions → ID UUID Generator for Databases and Microservices: IDs That Scale →

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