Developer Tools
UUID Generator
Generate random version 4 UUIDs instantly. Customize count and case.
UUIDs
Each UUID is a unique v4 (random) identifier. Copy the list and use as needed.
Developer Tools
Generate random version 4 UUIDs instantly. Customize count and case.
UUIDs
Each UUID is a unique v4 (random) identifier. Copy the list and use as needed.
A UUID is a 36-character alphanumeric string (with hyphens) that uniquely identifies an entity across systems without requiring a central registry. Unlike database auto-increment IDs, UUIDs are globally unique, making them essential for microservices, mobile apps, and APIs. Five standard UUID versions exist (v1–v5), each suited to different use cases: v1 uses timestamps, v4 uses randomness, and v5 uses hashing.
UUID generation depends on the version. UUID v4 (most common) generates a random 128-bit number and formats it as eight groups of hexadecimal digits separated by hyphens (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx). UUID v1 embeds the current timestamp and MAC address, making it sortable but less random. UUID v5 hashes a namespace and name using SHA-1, producing deterministic UUIDs where the same inputs always generate the same UUID. All versions produce the same 36-character string format.
| Input | Result | Notes |
|---|---|---|
| Generate v4 UUID | a1b2c3d4-e5f6-4789-9abc-def012345678 | Random UUID v4. Each generation produces a different value. Use for primary keys in PostgreSQL, MongoDB, or any database where uniqueness is critical. |
| Generate v1 UUID | 110e8400-e29b-41d4-a716-446655440000 | Time-based UUID v1 containing timestamp and MAC address. Sortable by creation time. Use when you need chronological ordering without a separate created_at column. |
| Generate v5 UUID with namespace 'api.example.com' and name 'user:12345' | 886313e1-3b8a-5372-9b90-0c9aee199e5d | Deterministic UUID v5. Same namespace and name always produce the same UUID. Use for session tokens, content hashes, or resource IDs that must be reproducible. |
UUID v4 is random and privacy-safe; use it by default. UUID v1 includes timestamp and MAC address, making it sortable by creation time but revealing device info. Choose v4 unless you specifically need chronological sorting without a separate timestamp column.
For v4 (random), collision probability is astronomically low—about 1 in 5.3 × 10^36. For v5 (hash-based), collisions are impossible if the same namespace and name are used. In practice, UUID collisions are not a concern.
Auto-increment IDs require a central database authority to assign the next number. UUIDs are generated anywhere without coordination, making them ideal for distributed systems, offline-first apps, and databases that may be merged or replicated.
Most languages have built-in UUID libraries: Python ('uuid.uuid4()'), JavaScript ('crypto.randomUUID()'), Java ('UUID.randomUUID()'), and C# ('Guid.NewGuid()'). Use the language's standard library instead of an online tool for production.
Yes, GUID (Globally Unique Identifier) is Microsoft's name for UUID. They're identical in structure and intent—GUID is just a Windows/C# convention. Newer systems prefer the term UUID.
No. UUIDs are not cryptographically random enough for secrets. Use them only as non-sensitive identifiers. For secrets, use a cryptographically secure random generator with at least 256 bits of entropy.