OpenMetrics

OpenMetrics is an open specification that formalizes and extends the Prometheus exposition format into a vendor-neutral standard for transmitting time-series metrics at scale. It defines exactly how a system exposes counters, gauges, histograms, and summaries so that any monitoring backend can scrape and interpret them the same way. The goal is a single, unambiguous wire format for metrics that no longer depends on one project’s implementation details.

• Prometheus lineage - It takes the widely-deployed Prometheus text format and makes it a documented standard rather than a de-facto one.
• Text and protobuf encodings - Metrics can be exposed as human-readable text or compact protobuf, covering both debuggability and efficiency.
• Typed metric families - Counters, gauges, histograms, and summaries are first-class, with explicit units and metadata attached to each series.
• Exemplars - Individual samples can carry trace references, linking a metric spike back to the specific request that caused it.

In real API operations, OpenMetrics is what a /metrics endpoint speaks so that request rates, error counts, and latency histograms can be scraped without custom adapters. Standardizing that surface means the same dashboards, alerting rules, and SLOs work across every service regardless of language or framework. Alongside OpenTelemetry, it forms the metrics half of a portable observability stack, and its exemplar support ties those metrics back to the traces that explain them.