Application Performance Monitoring (APM) platforms instrument running applications to capture code-level execution details — distributed traces, span timings, database query performance, cache hit rates, external dependency latency — so engineers can diagnose slow requests, identify bottlenecks, and track service-level performance across releases. Core capabilities include auto-instrumentation agents for common languages and frameworks, distributed trace context propagation, service-map visualization that shows call dependencies, database and dependency profiling, deployment-annotation correlation with performance changes, and AI-driven anomaly detection on response-time patterns. The category has converged with the broader Observability Platform market but retains a distinct motion around application-code-level performance analysis. Leading vendors include Dynatrace, New Relic, AppDynamics (Cisco), Instana (IBM), Datadog APM, and Elastic APM.