Free UUID Generator

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems without requiring a central authority to coordinate IDs. UUID v4 uses random number generation to create identifiers with 122 random bits, making collisions (duplicates) astronomically unlikely.

UUIDs follow the RFC 4122 standard and are formatted as 32 hexadecimal digits displayed in five groups separated by hyphens: 8-4-4-4-12, like 550e8400-e29b-41d4-a716-446655440000. The version and variant bits are fixed, while the remaining 122 bits are randomly generated.

How to Use This UUID Generator

1. Single UUID: Click "Generate New" to create one UUID v4
2. Bulk Generation: Click any number (1, 5, 10, 25, 50, 100) to generate multiple UUIDs at once
3. Copy: Click "Copy" next to any UUID to copy it to your clipboard
4. Download: When generating multiple UUIDs, click "Download All" to save them as a text file
5. Use: Paste UUIDs into your database schemas, API code, or configuration files

Why Use UUIDs?

For Databases

• Primary Keys: Use as primary keys in distributed databases (no auto-increment conflicts)
• Merge-Friendly: Perfect for databases that sync across devices (no ID collisions)
• Security: Non-sequential IDs prevent enumeration attacks
• Replication: Safe for multi-master database replication

For APIs and Microservices

• Request IDs: Track requests across distributed systems
• Correlation IDs: Link related operations in microservices architectures
• Resource Identifiers: Create unique IDs for resources without database lookups
• Idempotency Keys: Prevent duplicate API operations

For Application Development

• Session IDs: Generate unique session identifiers
• File Names: Create unique filenames to prevent overwrites
• Transaction IDs: Track financial transactions and payments
• Entity Keys: Identify entities in event sourcing and CQRS patterns

UUID Versions Explained

• UUID v1: Time-based, includes MAC address (can leak machine info)
• UUID v2: DCE Security version (rarely used)
• UUID v3: Name-based using MD5 hash
• UUID v4: Random (this tool) - most commonly used
• UUID v5: Name-based using SHA-1 hash
• UUID v6: Time-ordered, sortable (new standard)
• UUID v7: Unix timestamp-based, sortable (newest standard)

Why v4? UUID v4 is the most popular version because it's simple, stateless, and doesn't leak information about your system. It's perfect for most use cases where you need globally unique identifiers.

UUID Best Practices

• Database Indexing: Consider performance impact on large tables (UUIDs are larger than integers)
• Storage Format: Store as binary (16 bytes) instead of string (36 bytes) for efficiency
• Display Format: Always show with hyphens for readability (8-4-4-4-12)
• Generation Location: Generate on client-side to reduce server load
• Case Sensitivity: Treat as case-insensitive (use lowercase for consistency)
• Validation: Always validate UUID format before database insertion

Common Use Cases

For Web Developers

• User IDs: Identify users without sequential IDs
• Order Numbers: Generate unique order identifiers for e-commerce
• File Uploads: Create unique filenames for uploaded files
• Webhook IDs: Track webhook deliveries and retries

For Mobile Developers

• Offline Creation: Generate IDs on mobile devices before syncing to server
• Device IDs: Uniquely identify devices and installations
• Event Tracking: Track user events with unique event IDs

For DevOps Engineers

• Log Correlation: Link logs across distributed systems
• Build IDs: Uniquely identify CI/CD builds and deployments
• Container Names: Generate unique container and pod identifiers

Frequently Asked Questions

Are UUID v4 identifiers truly unique?

Yes, for all practical purposes. UUID v4 uses 122 random bits, creating 2^122 (5.3 × 10^36) possible combinations. The probability of generating a duplicate is so small it's considered impossible. According to the birthday paradox, you'd need to generate 2.71 quintillion (2.71 × 10^18) UUIDs to have a 50% chance of a collision.

Can I use UUIDs as database primary keys?

Yes, but with considerations. UUIDs work great as primary keys in distributed systems where multiple databases need to generate IDs independently. However, they have downsides: larger index size (16 bytes vs 4-8 bytes for integers), random insertion order can cause B-tree fragmentation, and slower joins compared to integer keys.

For best performance, use UUID v6 or v7 (time-ordered) which maintain sortability, or store UUIDs as binary instead of strings.

What's the difference between UUID and GUID?

UUID (Universally Unique Identifier) and GUID (Globally Unique Identifier) are the same thing. GUID is Microsoft's term for UUID. They both follow the RFC 4122 standard and are interchangeable. The tech industry generally uses "UUID" while Windows/.NET developers often use "GUID".

Should I generate UUIDs on the client or server?

Both are valid! Client-side generation (like this tool) reduces server load and works offline. It's perfect for mobile apps, offline-first applications, and distributed systems. Server-side generation ensures consistency and allows for auditing. Choose based on your architecture:

• Client-side: Offline apps, mobile, reduced server load
• Server-side: Centralized auditing, guaranteed uniqueness checks, database triggers

Are UUIDs secure for authentication tokens?

No. While UUIDs are unpredictable, they're not designed for security-critical applications like authentication tokens. Use dedicated cryptographic random number generators (CSPRNGs) for security tokens. UUIDs are perfect for identification, not authentication or authorization.

How do I store UUIDs efficiently in databases?

For best performance, store UUIDs as binary data (16 bytes) instead of strings (36 bytes):

• PostgreSQL: Use UUID data type (stores as 16 bytes)
• MySQL: Use BINARY(16) with conversion functions
• SQLite: Use BLOB type for binary storage
• MongoDB: Use BinData subtype 4 for UUIDs

Can I generate UUIDs in my programming language?

Yes! Every major programming language has UUID generation libraries:

• JavaScript: crypto.randomUUID() (Node 16+, all modern browsers)
• Python: import uuid; uuid.uuid4()
• Java: UUID.randomUUID()
• PHP: Ramsey\Uuid\Uuid::uuid4()
• Go: github.com/google/uuid package
• Ruby: SecureRandom.uuid