UUID Generator: The Complete Guide to UUIDs and GUIDs (2026)

UUID (Universally Unique Identifier) is a 128-bit identifier that's guaranteed to be unique across space and time. Whether you're building distributed systems, managing database records, or generating session tokens, UUIDs are the gold standard for unique identification.

Our free UUID Generator lets you create unique identifiers instantly. Generate single UUIDs or bulk batches up to 1000 at a time�all processed securely in your browser with zero server calls.

Anatomy of a UUID

A UUID consists of 32 hexadecimal characters, displayed in five groups separated by hyphens:

// UUID Format: 8-4-4-4-12
xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

// Where:
// M = Version (1, 4, 7, etc.)
// N = Variant (8, 9, a, or b)

// Example UUID v4:
f47ac10b-58cc-4372-a567-0e02b2c3d479

• 128 bits total � 32 hexadecimal characters
• Version digit � Position 13 indicates UUID version
• Variant digit � Position 17 indicates variant (RFC 4122)
• Case insensitive � Can be uppercase or lowercase

UUID Versions Explained

UUID v1 (Timestamp-based)

Generated using the current timestamp and MAC address of the machine. Provides ordering and uniqueness but reveals information about when and where it was created.

UUID v4 (Random)

The most commonly used version. Generated using cryptographically secure random numbers. Offers no temporal ordering but provides complete anonymity. Our generator uses the Web Crypto API for maximum security.

UUID v7 (Unix Epoch Time)

A newer version that combines timestamp ordering with randomness. The first 48 bits contain a Unix timestamp in milliseconds, making v7 UUIDs naturally sortable. Ideal for database primary keys where time-ordering improves index performance.

// UUID v1 - Timestamp + MAC Address
6ba7b810-9dad-11d1-80b4-00c04fd430c8

// UUID v4 - Random
f47ac10b-58cc-4372-a567-0e02b2c3d479

// UUID v7 - Timestamp + Random (sortable)
0188a6a9-3e7c-7b8a-85d3-2d6f8a9b1c0e

UUID vs GUID: What's the Difference?

There is no difference. GUID (Globally Unique Identifier) is simply Microsoft's term for UUID. Both follow the same RFC 4122 specification and produce identical 128-bit identifiers. Use whichever term is standard in your technology stack:

• UUID � Standard term, used in Java, Python, Linux, PostgreSQL
• GUID � Microsoft term, used in .NET, SQL Server, Windows

Common Use Cases

1. Database Primary Keys

UUIDs are perfect for distributed databases where multiple nodes generate IDs independently. Unlike auto-increment integers, UUIDs never collide during data merges or replication.

2. API Idempotency Keys

Include a UUID with API requests to ensure operations are processed exactly once. Payment gateways and financial systems rely heavily on this pattern.

3. Session Tokens

Generate secure, unguessable session identifiers. With 2^122 possible values, UUIDs are impossible to enumerate or predict.

4. File and Resource Naming

Avoid filename collisions when storing user uploads. Prefix files with UUIDs to ensure uniqueness across your entire system.

5. Distributed Tracing

Assign UUIDs to requests as they flow through microservices. This enables end-to-end tracing and debugging in complex distributed systems.

UUIDs in Databases

PostgreSQL

CREATE TABLE users (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    email VARCHAR(255) NOT NULL,
    created_at TIMESTAMP DEFAULT NOW()
);

MySQL

CREATE TABLE users (
    id CHAR(36) PRIMARY KEY DEFAULT (UUID()),
    email VARCHAR(255) NOT NULL
);

-- Or use BINARY(16) for better performance
CREATE TABLE users_optimized (
    id BINARY(16) PRIMARY KEY,
    email VARCHAR(255) NOT NULL
);

Programming with UUIDs

JavaScript

// Using Web Crypto API (recommended)
const uuid = crypto.randomUUID();
// "f47ac10b-58cc-4372-a567-0e02b2c3d479"

// Using uuid npm package
import { v4 as uuidv4 } from 'uuid';
const id = uuidv4();

Python

import uuid

# Generate UUID v4 (random)
new_uuid = uuid.uuid4()
# UUID('f47ac10b-58cc-4372-a567-0e02b2c3d479')

# Generate UUID v1 (timestamp)
timestamp_uuid = uuid.uuid1()

# Convert to string
uuid_string = str(new_uuid)

Java

import java.util.UUID;

// Generate random UUID
UUID uuid = UUID.randomUUID();

// Convert to string
String uuidString = uuid.toString();

// Parse UUID from string
UUID parsed = UUID.fromString("f47ac10b-58cc-4372-a567-0e02b2c3d479");

Frequently Asked Questions

Code Formatter � 2026. Professional developer tools built with privacy and performance in mind.