Grafana Cloud: Synthetic Monitoring custom labels change schema

Grafana Labs announced on 10 September 2026, on the official blog, a change to the custom label schema in Synthetic Monitoring on Grafana Cloud. It affects users who run synthetic checks to monitor endpoints, APIs or services and organise them with custom labels for team, environment or service.

What's changing

Until now, custom labels defined on a check existed only on the sm_check_info metric, with a label_ prefix added automatically: a label called team became label_team. To filter a dashboard, set an alert or allocate costs by service, you had to join sm_check_info with the check metric you actually wanted to query, and remember that team was actually rendered as label_team.

With the update, labels defined on a check are now attached to all metrics generated by that check, not just sm_check_info, and the prefix disappears: the label_ prefix is removed, labels appear as written, for example a label called team appears as team, not as label_team.

The migration: three phases

The transition happens in three stages, manageable from the Label migration tab in the Synthetic Monitoring app: Prefixed, where labels exist only on sm_check_info with the label_ prefix; Dual-write, where both prefixed and non-prefixed labels are written in parallel per metric; and Un-prefixed, where prefixed labels are retired and only direct labels remain.

Before starting the migration, check that custom labels don't collide with the list of system-reserved names: the system rejects the migration if any label matches reserved values, and running the steps requires administrator access.

On costs, Grafana Labs clarifies that the migration does not increase cardinality or costs: the period when prefixed and non-prefixed series coexist during dual-write is absorbed into billing at the 95th percentile and is not charged as additional active series, and no historical data is lost.

Deadline and what happens next

The migration window is open immediately, but Grafana Labs sets a deadline: migration must be completed by 1 March 2027 to ensure that custom dashboards, SLOs, alerts and queries referencing Synthetic Monitoring metrics don't break. After that date, support for the old prefixed schema ends and any stack not yet migrated will be migrated automatically by Grafana Labs, with less control over timing than a user-planned migration.

If you don't use custom labels in Synthetic Monitoring, you don't need to do anything: if custom labels aren't used in Synthetic Monitoring, nothing changes and no action is required.