UUID Generator (v4)

Generate random universally unique identifiers instantly

100% client-side · your data never leaves your browser
⚡
Click "Generate" to create UUIDs (v4)
💡 About UUID v4: Universally Unique Identifiers (UUIDs) are 128-bit numbers used to uniquely identify information. Version 4 UUIDs are randomly generated and have a collision probability of approximately 1 in 5.3×10³⁶.

📖 How to Use

  1. Enter the number of UUIDs you want to generate (1-10,000) or use quick generate buttons
  2. Click "Generate" to create random UUIDs
  3. Each UUID appears in a separate card with its own copy button
  4. Use "Copy All" to copy all generated UUIDs (one per line)
  5. Click "Download" to save all UUIDs as a text file
  6. Click "Clear" to reset and start fresh

About the UUID Generator

The UUID Generator is a free, browser-based tool that instantly creates RFC 4122 compliant UUID v4 (random) identifiers. UUIDs are essential for modern application development, providing globally unique identifiers without requiring central coordination. This tool uses cryptographically secure random number generation (crypto.randomUUID() API) to ensure high-quality randomness and uniqueness. Whether you need a single UUID for a database record or thousands for bulk operations, this tool handles it all locally in your browser with complete privacy.

Key Features:

  • Instant UUID v4 generation with cryptographically secure randomness
  • Bulk generation support (1-10,000 UUIDs at once)
  • Individual copy buttons for each generated UUID
  • Copy all UUIDs at once (one per line, ready for use)
  • Download UUIDs as .txt file for offline use or database seeding
  • 100% client-side generation - no server requests or tracking

Common Use Cases:

  • Database Primary Keys: Generate unique IDs for database records in distributed systems (PostgreSQL UUID, MongoDB ObjectID replacement)
  • API Development: Create unique request IDs, transaction IDs, and correlation IDs for microservices and API logging
  • Session Management: Generate secure, unpredictable session tokens for user authentication systems
  • File Management: Create unique file names for uploads to prevent conflicts and enable distributed storage
  • Testing & Seeding: Bulk generate UUIDs for database seeding, test data creation, and QA automation

UUID Usage Examples & Implementation Patterns

PostgreSQL Database Primary Key

-- Create table with UUID primary key:
CREATE TABLE users (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  email VARCHAR(255) UNIQUE NOT NULL,
  name VARCHAR(255),
  created_at TIMESTAMP DEFAULT NOW()
);

-- Insert with explicit UUID:
INSERT INTO users (id, email, name)
VALUES ('550e8400-e29b-41d4-a716-446655440000', '[email protected]', 'John Doe');

Use case: Distributed database systems where multiple servers generate records independently

JavaScript/TypeScript UUID Generation

// Modern browsers (built-in):
const uuid = crypto.randomUUID();
// Output: "550e8400-e29b-41d4-a716-446655440000"

// Node.js (v14.17+):
import { randomUUID } from 'crypto';
const uuid = randomUUID();

// React component example:
function CreateUser() {
  const handleSubmit = () => {
    const userId = crypto.randomUUID();
    fetch('/api/users', {
      method: 'POST',
      body: JSON.stringify({ id: userId, ...userData })
    });
  };
}

Use case: Client-side UUID generation for frontend applications and API requests

API Request Correlation ID

// Express.js middleware:
app.use((req, res, next) => {
  req.correlationId = crypto.randomUUID();
  res.setHeader('X-Correlation-ID', req.correlationId);
  logger.info(`[$${req.correlationId}] $${req.method} $${req.path}`);
  next();
});

// Trace across microservices:
fetch('https://api.service2.com/data', {
  headers: { 'X-Correlation-ID': correlationId }
});

Use case: Tracing requests across distributed microservices for debugging and monitoring

File Upload with Unique Names

// Node.js file upload handler:
import { extname } from 'path';

function handleFileUpload(file) {
  const uuid = crypto.randomUUID();
  const ext = extname(file.originalname);
  const filename = `$${uuid}$${ext}`;

  // S3/Cloud Storage:
  await uploadToS3(`uploads/$${filename}`, file.buffer);

  return {
    id: uuid,
    url: `https://cdn.example.com/uploads/$${filename}`
  };
}

Use case: Prevent filename conflicts in cloud storage and CDN uploads

Session Token Generation

// Session management:
function createSession(userId) {
  const sessionId = crypto.randomUUID();
  const expiresAt = Date.now() + (24 * 60 * 60 * 1000); // 24 hours

  await redis.set(`session:$${sessionId}`, JSON.stringify({
    userId,
    createdAt: Date.now(),
    expiresAt
  }));

  return sessionId;
}

// Verify session:
const session = await redis.get(`session:$${sessionId}`);
if (!session) throw new Error('Invalid session');

Use case: Secure session token generation for authentication systems

MongoDB Document ID

// Mongoose schema with UUID:
import { randomUUID } from 'crypto';

const userSchema = new Schema({
  _id: {
    type: String,
    default: () => randomUUID()
  },
  email: String,
  name: String
});

// Create document with UUID:
const user = new User({
  email: '[email protected]',
  name: 'John Doe'
});
await user.save();
// _id: "550e8400-e29b-41d4-a716-446655440000"

Use case: Replace MongoDB ObjectIDs with UUIDs for cross-database compatibility

❓ Frequently Asked Questions

What is a UUID and how does it work?

UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. It's displayed as 32 hexadecimal digits in the format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (8-4-4-4-12 format). UUIDs are globally unique without requiring a central coordination authority, making them ideal for distributed systems where generating IDs independently is essential.

What is UUID v4 and why use it?

UUID version 4 uses random or pseudo-random numbers for generation, with 122 random bits. It's the most commonly used UUID version because it's simple to generate, requires no coordination, and has an extremely low collision probability (approximately 1 in 5.3×10³⁶). This tool generates RFC 4122 compliant UUID v4 identifiers using cryptographically secure randomness (crypto.randomUUID() in modern browsers).

Are generated UUIDs truly unique? Can duplicates occur?

While no system can guarantee absolute uniqueness, UUID v4 has such a large address space (2¹²⁸ possible values) that the probability of generating a duplicate is astronomically low. To put it in perspective, you'd need to generate 1 billion UUIDs per second for 85 years to have a 50% chance of a single collision. For practical purposes, they can be considered unique for database records, session IDs, and file names.

When should I use UUIDs instead of auto-incrementing IDs?

Use UUIDs for database primary keys in distributed systems (where multiple servers generate IDs), session identifiers, transaction IDs, file names, API request IDs, public-facing IDs (harder to guess than sequential numbers), and any scenario where you need unique identifiers without central coordination. Use auto-incrementing IDs when you need guaranteed sequential ordering or when dealing with single-database systems where coordination is easy.

Can I generate multiple UUIDs at once?

Yes! This tool supports bulk generation up to 10,000 UUIDs. Use the quick generate buttons (1, 5, 10, 50, 100) or enter a custom amount. You can copy all UUIDs at once (one per line) or download them as a .txt file. Bulk generation is useful for database seeding, testing, and generating multiple unique identifiers at once.

What's the difference between UUID and GUID?

UUID (Universally Unique Identifier) and GUID (Globally Unique Identifier) are essentially the same thing. UUID is the term used in RFC 4122 and most programming languages, while GUID is Microsoft's term used in .NET and Windows systems. Both use the same 128-bit format and generation algorithms. This tool generates standard UUIDs that work everywhere.

Are UUIDs secure for sensitive applications?

UUID v4 uses cryptographically secure random number generation, making them unpredictable and suitable for security-sensitive applications like session tokens and API keys. However, they should not be your only security measure. For authentication tokens, combine UUIDs with proper encryption, HTTPS, and token expiration. Never rely on UUID unpredictability alone for security.

Can I use UUIDs as database primary keys?

Yes, UUIDs work well as database primary keys, especially in distributed systems. Benefits include: no central coordination needed, harder to guess than sequential IDs, can be generated client-side, and work across multiple databases/servers. Drawbacks include: larger storage size (16 bytes vs 4-8 bytes for integers), slightly slower indexing, and less human-friendly. Most modern databases (PostgreSQL, MySQL, MongoDB) have excellent UUID support.

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