UUID vs GUID
Summary
Definition: UUID is a standardized 128-bit identifier; GUID is Microsoft's compatible name for it.
Why it matters: Correct UUID choices improve interoperability, performance, and data safety.
Pitfall: UUIDs provide uniqueness, not security.
UUID is the standardized identifier defined by the IETF. GUID is Microsoft's name for the same
128-bit identifier format, and the two are fully interoperable.
- UUID
- Standardized 128-bit identifier defined by the IETF.
- GUID
- Microsoft term for a UUID-compatible identifier.
- Version
- Indicates the UUID generation method.
- Variant
- Defines the UUID layout and compatibility.
UUID format
The canonical UUID string has 32 hexadecimal characters displayed as 8-4-4-4-12 with hyphens.
Many systems accept non-hyphenated forms, but the hyphenated form is the canonical representation.
Common mix-up: UUIDs and GUIDs are different standards. They use the same format and values.
UUID versions
| Version | Best for |
|---|---|
| v1 | Legacy systems using time and node data |
| v4 | Random, general-purpose identifiers |
| v5 | Stable, name-based identifiers |
| v7 | Time-ordered identifiers for databases |
Most modern systems use the RFC 4122 variant defined by the IETF.
Quick example
A randomly generated UUID using the canonical 8-4-4-4-12 format.
f47ac10b-58cc-4372-a567-0e02b2c3d479Try it yourself
- Generate a UUID using the standard tool.
- Use UUID v7 when ordering or indexing matters.
Practical check
- Generate a UUID.
- Confirm the 8-4-4-4-12 pattern.
- Store UUIDs consistently in lowercase.
FAQ
Are GUID and UUID the same? Yes. GUID is Microsoft's name for a UUID-compatible identifier.
Which UUID version should I use? Use v4 for random IDs, v7 for ordered IDs, and v5 for deterministic name-based IDs.
Are UUIDs secure? No. UUIDs are identifiers, not secrets.