Variables

$varname substitution. Three types:

static

A fixed list of values. {name:"env", options:["prod","staging","dev"]}. Good for rarely changing choices.

label_values

Loads label values from an existing metric. {name:"host", metric:"system_cpu_usage_percent", label:"host"}. Refreshed on every dashboard load.

query (new)

Runs an arbitrary PromQL query and pulls the given label's values out of the resulting vector. {name:"job", expr:"group by (job) (up)", label:"job"}.

Substitution happens on the client: $varname and ${varname} in metric or filter values are replaced before the request. The server is variable-agnostic, so variables cannot be used in alert rules (use saved filters instead).