MC1185445 – M365 Change Digest

One-line summary

Microsoft Purview adds Classifier Simulation Mode, letting admins test custom classifiers on production data before publishing and access health insights in the compliance portal.

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Details

RoadmapIds

523201

Summary

Microsoft Purview introduces Classifier Simulation Mode to test custom classifiers on production data before publishing, reducing false positives and improving performance. Available from early 2026, it provides health insights in the compliance portal, allowing admins to monitor, simulate, and optimize classifiers with role-based access control.

Platforms

Web

Body (from Message Center)

Updated December 16, 2025: We have made a minor correction. Thank you for your patience.

[Introduction]

Microsoft Purview is introducing Classifier Simulation Mode, the first phase of the broader Classifier Health Monitoring Platform. This new capability allows admins to test and validate custom classifiers on production data before publishing. Simulation Mode enables admins to optimize classifier logic before deployment, helping in reducing false positives, scanning latency, and noisy matches. Admins will access simulation controls and classifier health insights directly in the Microsoft Purview compliance portal, making it easier to monitor and improve classifier performance in one centralized location.

This message is associated with Roadmap ID 523201.

[When this will happen:]

Targeted Release (Worldwide): Rollout begins early November 2025, completes by early December 2025.
General Availability (Worldwide): Rollout begins late February 2026, completes by late March 2026.

[How this affects your organization:]

Who is affected: Admins managing Microsoft Purview Information Protection and custom sensitive information types (SITs).
What will happen:
- By default, the feature will be available to all tenants.
- Admins will see a new option to simulate a custom classifier before publishing.
- Simulation is optional — admins can choose to simulate or publish directly.
- Classifiers published without simulation will still be monitored for performance and flagged if unhealthy.
- Classifier health insights will be available in the Microsoft Purview compliance portal, helping admins identify and remediate inefficient classifiers.
- Inefficient classifiers may be automatically disabled to maintain system performance.

[What you can do to prepare:]

Admins can begin using Simulation Mode once available; no onboarding or training is required.
Once the feature is available:
- Review classifier health insights in the compliance portal.
- Monitor any SITs flagged as unhealthy and adjust logic as needed.
- Consider simulating classifiers before publishing to reduce risk of false positives or performance issues.

[Compliance considerations:]

Question	Explanation
Does the change alter how existing customer data is processed, stored, or accessed?	Classifiers will be simulated on production data, but not published, allowing analysis without altering data classification outcomes.
Does the change introduce or significantly modify AI/ML or agent capabilities that interact with or provide access to customer data?	Introduces classifier health monitoring logic that evaluates classifier performance and flags inefficiencies.
Does the change modify how admins can monitor, report on, or demonstrate compliance activities?	Adds new health insights and monitoring capabilities for custom classifiers in the compliance portal.
Does the change include an admin control and, can it be controlled through Entra ID group membership?	Simulation and publishing options are available to admins; access can be managed via role-based permissions.

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