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UUID / GUID Generator

Generate cryptographically random UUID v4 identifiers — or bulk-generate hundreds at once. Color-coded for easy reading.

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Bulk UUID Generator

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UUID Validator

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What is a UUID?

A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit label used to uniquely identify information in computer systems. UUIDs are standardized in RFC 4122 and represented as a 32-character hexadecimal string in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

UUID Versions

  • UUID v4 (Random) — most commonly used. Generated from cryptographically random bits. The probability of collision is negligible (1 in 2¹²² ≈ 5.3 × 10³⁶).
  • UUID v1 (Time-based) — incorporates the current timestamp and node ID. Monotonically increasing; useful for sorted storage in databases.
  • UUID v5 (Name-based SHA-1) — deterministic: same namespace + name always produces the same UUID. Useful for content-addressable identifiers.

Common Use Cases

  • Database primary keys (especially in distributed systems)
  • Session tokens and correlation IDs
  • File names for uploaded content
  • Tracking events in microservices and APIs
  • Idempotency keys for API requests

Frequently Asked Questions

How unique is a UUID v4?
Extremely unique. UUID v4 uses 122 bits of randomness. Generating 1 billion UUIDs per second for the next 100 years gives a collision probability of approximately 50% — meaning in practice, collisions are not a concern for any real-world application.
UUID vs GUID — what's the difference?
They refer to the same thing. "GUID" (Globally Unique Identifier) is Microsoft's term; "UUID" (Universally Unique Identifier) is the open standard (RFC 4122). They use the same format and are interchangeable in most contexts.
Should I use UUID as a database primary key?
UUIDs work well as primary keys, especially in distributed systems where you can't use auto-increment. The tradeoffs: UUIDs are larger (16 bytes vs 4-8 bytes for integers) and random UUIDs cause index fragmentation. Consider UUID v7 (time-ordered) or ULID for better database performance.