# `Prometheus.InvalidLabelNameError`
[🔗](https://github.com/prometheus-erl/prometheus.ex/blob/v5.1.0/lib/prometheus/error.ex#L67)

Raised when label `name` is invalid i.e. can't be represented as printable utf-8 string
that matches `^[a-zA-Z_][a-zA-Z0-9_]*$` regular expression or starts with `__`.

Metric can impose further restrictions on label names.

# `message`

---

*Consult [api-reference.md](api-reference.md) for complete listing*