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 (Universally Unique Identifier) is a 128-bit number used to uniquely identify data across distributed systems, APIs, and databases. Use this tool to generate UUIDs in seconds—perfect for creating primary keys, session tokens, resource identifiers, and ensuring no collision across millions of records.
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.