# Labels in Grafana Alerting
<a name="v12-alerting-overview-labels-alerting"></a>

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This documentation topic is designed for Grafana workspaces that support **Grafana version 12.x**.  
For Grafana workspaces that support Grafana version 10.x, see [Working in Grafana version 10](using-grafana-v10.md).  
For Grafana workspaces that support Grafana version 9.x, see [Working in Grafana version 9](using-grafana-v9.md).  
For Grafana workspaces that support Grafana version 8.x, see [Working in Grafana version 8](using-grafana-v8.md).

This topic explains why labels are a fundamental component of alerting.
+ The complete set of labels for an alert is what uniquely identifies an alert within Grafana alerts.
+ The Alertmanager uses labels to match alerts for silences and alert groups in notification policies.
+ The alerting UI shows labels for every alert instance generated during evaluation of that rule.
+ Contact points can access labels to dynamically generate notifications that contain information specific to the alert that is resulting in a notification.
+ You can add labels to an [alerting rule](v12-alerting-configure.md). Labels are manually configurable, use template functions, and can reference other labels. Labels added to an alerting rule take precedence in the event of a collision between labels (except in the case of Grafana reserved labels, see below for more information).

## External Alertmanager compatibility
<a name="v12-alerting-overview-labels-alerting-external"></a>

Grafana’s built-in Alertmanager supports both Unicode label keys and values. If you are using an external Prometheus Alertmanager, label keys must be compatible with their [data model](https://prometheus.io/docs/concepts/data_model/#metric-names-and-labels). This means that label keys must only contain **ASCII letters**, **numbers**, as well as **underscores** and match the regex `[a-zA-Z_][a-zA-Z0-9_]*`. Any invalid characters will be removed or replaced by the Grafana alerting engine before being sent to the external Alertmanager according to the following rules:
+ `Whitespace` will be removed.
+ `ASCII characters` will be replaced with `_`.
+ `All other characters` will be replaced with their lower-case hex representation. If this is the first character it will be prefixed with `_`.

**Note**  
If multiple label keys are sanitized to the same value, the duplicates will have a short hash of the original label appended as a suffix.

## Grafana reserved labels
<a name="v12-alerting-overview-labels-alerting-reserved"></a>

**Note**  
Labels prefixed with `grafana_` are reserved by Grafana for special use. If a manually configured label is added beginning with `grafana_` it will be overwritten in case of collision.

Grafana reserved labels can be used in the same way as manually configured labels. The current list of available reserved labels are:


| Label | Description | 
| --- | --- | 
| grafana\$1folder | Title of the folder containing the alert. |