A 128-bit value that is unique, used for things such as session IDs or the default names given to workspaces.
Also called globally unique identifier.
In the Ultra Transcenders books
AI-200SC-200AZ-802DP-600DP-700SC-401MD-102DP-800ALZ
Each book explains GUID in context, with comparison tables and the common traps.
Related terms
- Network Message ID
Defender for Office 365 tools and advanced hunting use this GUID to pick out a particular email. Its value comes from a message header named X-MS-Exchange-Organization-Network-Message-Id.
- Partitioning policy
A KQL policy set on an eventhouse table to reorganise data extents once ingestion has finished, either by hashing one string or guid column or by splitting time into evenly sized datetime ranges. Without it, ingestion time determines grouping, and Microsoft Learn recommends using it in just a handful of particular query scenarios.
- Service key
The GUID identifying an ExpressRoute circuit, which you pass to the connectivity provider. It is not a secret, and charges begin as soon as it is issued.
- uniqueidentifier
A data type holding a 16-byte GUID. Values from
NEWID()are random and cause fragmentation in a clustered index, whileNEWSEQUENTIALID()produces values that keep increasing.