Generate cryptographically random UUID v4 identifiers. Bulk generate, customize format, and copy instantly.
A UUID (Universally Unique Identifier), also known as GUID (Globally Unique Identifier), is a 128-bit identifier that is guaranteed to be unique across all devices and time. UUID v4 uses random numbers, making collisions practically impossible — the probability of generating two identical UUIDs is about 1 in 5.3×10^36.
A standard UUID looks like: 550e8400-e29b-41d4-a716-446655440000
It consists of 32 hexadecimal digits displayed in 5 groups separated by hyphens: 8-4-4-4-12. For UUID v4, the third group always starts with 4 (version), and the fourth group starts with 8, 9, a, or b (variant).
| Version | Method | Use Case |
|---|---|---|
| v1 | Timestamp + MAC address | When ordering matters |
| v3 | MD5 hash of namespace + name | Deterministic from input |
| v4 | Random (most common) | General purpose unique IDs |
| v5 | SHA-1 hash of namespace + name | Deterministic (more secure than v3) |
Theoretically yes, but practically no. With UUID v4, you'd need to generate about 2.71 quintillion UUIDs to have a 50% probability of one collision. You're more likely to be struck by a meteorite.
UUIDs are better for distributed systems where multiple servers need to generate unique IDs independently. Auto-increment is simpler and more efficient for single-database applications.