What is the difference between client libraries and exporters?

The fundamental difference betweenPrometheus client librariesandexporterslies inhowandwherethey are used.

Client librariesare integrated directly into theapplication’s codebase. They allow developers toinstrumenttheir own code to define and expose custom metrics. Prometheus provides official client libraries for multiple languages, including Go, Java, Python, and Ruby.

Exporters, on the other hand, arestandalone processesthat run alongside the applications or systems they monitor. They use client libraries internally to collect and expose metrics from software that cannot be instrumented directly (e.g., operating systems, databases, or third-party services). Examples include the Node Exporter (for system metrics) and MySQL Exporter (for database metrics).

Thus, exporters are typically used forexternal systems, while client libraries are used forself-instrumented applications.