UUID Generator
Generate standard UUID v4 identifiers for your applications and databases. Fast, random, and unique.
UUID Generator
Generate UUID v4 identifiers locally. Choose quantity and copy results.
What is a UUID?
A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit number used to uniquely identify information in computer systems. UUIDs are standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE).
A standard UUID looks like this: 550e8400-e29b-41d4-a716-446655440000
The beauty of UUIDs is that they can be generated independently without a central coordinating authority, yet the probability of duplication is so infinitesimally small that it's considered effectively zero for practical purposes.
UUID Structure
A UUID consists of 32 hexadecimal digits displayed in 5 groups separated by hyphens:
xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx - Total length: 36 characters (32 hex + 4 hyphens)
- M indicates the UUID version (4 for random)
- N indicates the variant (usually 8, 9, A, or B)
- Hexadecimal digits: 0-9 and a-f
UUID Versions Explained
Version 1: Time-based
Generated from timestamp and MAC address of the generating computer.
⚠️ Privacy Risk: Can reveal device identity and creation time
Version 4: Random (Our Generator) ✅
Generated using random or pseudo-random numbers.
✨ Recommended: Most secure, no personally identifiable information, widely supported
Version 5: Name-based (SHA-1)
Generated from namespace and name using SHA-1 hash.
Use case: Deterministic UUIDs (same input always generates same UUID)
Why we generate V4: Version 4 is the most common and recommended for general use. It's completely random, doesn't leak any information about your system, and is accepted everywhere.
Common UUID Use Cases
- Database Primary Keys: UUIDs eliminate auto-increment ID collision in distributed databases
- Session IDs: Unique identifiers for user sessions in web applications
- File Names: Generate unique filenames for uploaded files to avoid conflicts
- API Request IDs: Track requests across microservices and logs
- Message Queue IDs: Uniquely identify messages in queuing systems
- Transaction IDs: Track financial or database transactions
- Resource Identifiers: Identify resources in RESTful APIs
- Security Tokens: Generate unique tokens for password resets or email verification
UUID vs Auto-Increment IDs
| Feature | UUID | Auto-Increment |
|---|---|---|
| Uniqueness | Globally unique | Unique per table |
| Generation | Client or server | Server only |
| Distributed Systems | Excellent | Problematic |
| Storage Size | 16 bytes | 4-8 bytes |
| Human Readable | No | Yes (1, 2, 3...) |
| Security | Non-sequential, unpredictable | Sequential, predictable |
How Unique Are UUIDs Really?
UUIDs have 2^122 possible values (approximately 5.3 × 10^36). To put this in perspective:
- If every human on Earth (8 billion) generated 1 billion UUIDs per second, it would take 2 trillion years to have a 50% chance of a collision
- You could assign a UUID to every atom in a trillion planets and still have plenty left over
- The probability of collision is 0.00000000000000000000000000000006%
Bottom line: For all practical purposes, UUIDs are unique. You're more likely to win the lottery jackpot 10 times in a row than generate a duplicate UUID.
Frequently Asked Questions
What is a UUID? ▼
A 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 groups (8-4-4-4-12). The probability of generating duplicate UUIDs is so astronomically low (1 in 5.3 × 10^36) that it's considered practically zero for all real-world purposes.
What's the difference between UUID versions? ▼
UUID v1 uses timestamp and MAC address (can reveal device info and creation time). UUID v4 (what this tool generates) uses random numbers, providing better privacy and security. UUID v5 uses namespace and name hashing for deterministic generation. V4 is the most commonly used and recommended for general purposes.
Are UUIDs truly unique globally? ▼
Yes, for all practical purposes. While it's theoretically possible to generate duplicates, the probability is so infinitesimally low that it never happens in practice. You'd need to generate billions of UUIDs per second for thousands of years to have even a tiny chance of collision. Major companies like Microsoft, Amazon, and Google rely on UUIDs for critical systems.
Can I use UUIDs as database primary keys? ▼
Absolutely! UUIDs make excellent primary keys, especially in distributed systems or microservices architectures. Benefits: globally unique (no coordination needed between databases), can be generated client-side, non-sequential (better security), and no collision risk when merging databases. The only downside is slightly larger storage size (16 bytes vs 4-8 for integers).
What format should I use - with or without hyphens? ▼
Standard format (8-4-4-4-12 with hyphens like `550e8400-e29b-41d4-a716-446655440000`) is more readable and universally recognized. Use this for APIs, logs, and display. Compact format (32 hex digits without hyphens) is shorter by 4 characters and useful for URLs, barcodes, or constrained storage. Most systems accept both formats.