UUID Generator
Generate random v4 UUIDs instantly. Batch generate up to 50 at once, validate existing UUIDs, and format in multiple styles.
How many?
Output format
UUID Versions
| Version | Algorithm | Common Use Cases | Type |
|---|---|---|---|
| v1 | Timestamp + MAC address | Sortable IDs, time-ordered databases | Random |
| v2 | DCE Security (POSIX UID) | Legacy POSIX systems (rare) | Random |
| v3 | MD5 hash (namespace + name) | Reproducible IDs from a name (legacy) | Deterministic |
| v4 | Random (122 random bits) | Database primary keys, API request IDs, session tokens | Random |
| v5 | SHA-1 hash (namespace + name) | Reproducible IDs from a name (preferred over v3) | Deterministic |
Frequently Asked Questions
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify information in computer systems. It is formatted as 32 hexadecimal digits in the pattern xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (e.g. 550e8400-e29b-41d4-a716-446655440000). There are five versions (v1–v5) defined in RFC 4122, each generated differently. UUIDs are designed so that no central authority is needed — two independently generated UUIDs will almost certainly be different.
UUID v1 is generated from the current timestamp plus the MAC address of the generating machine, making it time-ordered and traceable to its origin — useful for distributed databases that need sortable IDs, but it exposes the generating machine's identity. UUID v4 is generated from 122 random bits using a cryptographically secure random number generator, making it unpredictable and privacy-preserving. For most applications — database primary keys, API request IDs, session tokens — v4 is the recommended choice.
UUID v4 uses 122 random bits, giving 2^122 (about 5.3 × 10^36) possible values. The probability of generating two identical v4 UUIDs is so small it is effectively zero for any practical purpose — you would need to generate 1 billion UUIDs per second for 100 years to have even a 50% chance of a single collision. While not mathematically guaranteed to be unique, UUIDs are considered universally unique in practice and are widely used as primary keys in distributed systems precisely because they require no central coordination.
Use UUID v3 or v5 when you need a deterministic (repeatable) UUID derived from a name — for example, generating the same UUID for the same URL or email address every time. v5 uses SHA-1 hashing and is preferred over v3 (MD5). Both require a namespace UUID plus a name string and will always produce the same output for the same inputs. This is useful for content-addressed storage, mapping external IDs to UUIDs, or generating stable identifiers for named resources without storing a lookup table.