Free Online UUID / GUID Generator

Instantly create UUIDs (Universally Unique Identifiers) in versions v1, v4, and v5. All generation runs locally in your browser, ensuring privacy, security, and speed for developers, databases, and distributed systems.

UUID / GUID Generator

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UUID FAQ

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems.

What are UUID versions?

UUIDs have multiple versions: v1 (timestamp + MAC), v4 (random), and v5 (namespace + name). Each suits different needs.

Which UUID version should I use?

UUID v4 is the most common. Use v1 for time-ordering and v5 when deterministic values are required.

Are UUIDs truly unique?

Yes, the probability of collision is extremely low, especially with v4, making them practically unique.

Can UUIDs be guessed?

UUID v1 may reveal system details. UUID v4 is random and much harder to predict.

What’s the difference between UUID and GUID?

UUID and GUID are functionally the same. UUID is the standard, GUID is Microsoft's naming.

About UUIDs

Understanding UUIDs (Universally Unique Identifiers)

UUIDs, or Universally Unique Identifiers, are 128-bit values designed to guarantee global uniqueness across systems, databases, and applications. A UUID is typically displayed as a 36-character string that includes 32 hexadecimal digits separated by - hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000).

Why Use UUIDs?

Global uniqueness — no central authority needed to avoid collisions.
Scalability — ideal for distributed systems and microservices.
Database safety — prevents conflicts when merging data.
Versatility — can be random, time-based, or deterministic.

Different Versions of UUIDs

UUID v1: Based on timestamp and MAC address. Sequential but may leak hardware info.
UUID v4: Purely random. Most popular for APIs, databases, and sessions.
UUID v5: Deterministic, generated from a namespace + name via SHA-1.

UUIDs in Practice

Databases: Primary keys in PostgreSQL, MongoDB, MySQL.
APIs: Request identifiers for tracing.
Authentication: Session tokens and secure IDs.
Blockchain: Resource identifiers in DApps.
Filesystem: Unique IDs for files and objects.

Best Practices

Use UUID v4 for most apps where randomness is needed.
Use UUID v5 when deterministic IDs are required.
Avoid UUID v1 unless legacy compatibility demands it.
Don’t treat UUIDs as secrets — combine with cryptographic randomness for secure tokens.