- Universally Unique Identifier
- 128-bit number — 32 hex digits
- Probability of collision is practically zero
- Used as database primary keys, session IDs, file names and API tokens
- Version 4 — randomly generated. Most common. Use for almost everything.
- Version 1 — based on timestamp + MAC address. Sortable by time.
- Nil — all zeros. Used as a placeholder or default value.
- Database primary keys
- Session & auth tokens
- File & upload naming
- API request IDs
- Idempotency keys
- Distributed system IDs
How to use the UUID Generator
Choose your UUID version — Version 4 for a random UUID (most common), Version 1 for a timestamp-based UUID, or Nil for all zeros. Select your preferred format and the quantity you need. Click Generate and copy individual UUIDs or use Copy All to grab the full list.
Frequently Asked Questions
A UUID (Universally Unique Identifier) is a 128-bit number formatted as 32 hexadecimal characters separated by hyphens, like 550e8400-e29b-41d4-a716-446655440000. The probability of two randomly generated UUIDs being identical is so small it is considered practically impossible.
Version 4 UUIDs are randomly generated — each one is entirely unpredictable. Version 1 UUIDs are based on the current timestamp and the device MAC address, which means they can be sorted chronologically. Use v4 for most purposes and v1 when you need sortable IDs.
UUIDs are used as database primary keys, session and authentication tokens, file upload names, API request identifiers and idempotency keys. They allow multiple servers to generate unique IDs simultaneously without a central coordinator.
UUID and GUID (Globally Unique Identifier) are the same thing. GUID is the name Microsoft uses for the same standard. They are interchangeable and formatted identically.