UUID Generator
Generate RFC 4122 compliant UUID v4 identifiers.
d5306be0-052e-4fc4-a437-4a155bc0db8a0a59b96b-e548-4801-8ea0-f51ec2d09cf2c2f9dd22-70fc-4c6b-a9be-dbdd41efdf143a4117ab-9730-46ba-acf9-91d16b2bf51e5430201b-16a8-4274-a6b8-f7676cc93662About This Tool
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify information. UUID v4 is randomly generated, making collisions practically impossible. It's the most common version used in software development.
When to Use
- Database primary keys when you need IDs generated client-side without a round-trip to the server.
- Correlation IDs for distributed system request tracing.
- Filenames for uploaded assets to avoid name collisions.
- Idempotency keys for payment APIs.
Practical Examples
v4 Format550e8400-e29b-41d4-a716-446655440000 (8-4-4-4-12 hex character groups)
Version ByteThe 13th character is always '4' for UUID v4. The 17th is always '8', '9', 'a', or 'b'.
Common Mistakes to Avoid
- Using sequential integers as IDs in distributed systems — they create race conditions and ordering issues across nodes.
- Storing UUIDs as strings in a database instead of native UUID type (wastes 2× space).
Frequently Asked Questions
Q. How unique is UUID v4?A. The probability of generating a duplicate in 1 billion UUIDs per second for 100 years is about 50%. In practice, collisions are virtually impossible.
Q. Is UUID v4 secure?A. UUIDs are not cryptographically secure random numbers. Do not use them as auth tokens or session IDs — use crypto.getRandomValues or similar for security contexts.