Checkmk Raw
Nagios-descended infrastructure monitoring with auto-discovery, pre-built service checks, and a polished web UI. Raw edition is GPL-2.0.
All-in-One
Coroot
eBPF-based APM for Kubernetes. Zero-instrumentation service maps and SLO dashboards.
HyperDX
Open-source Datadog alternative that correlates logs, metrics, traces, and session replays in one UI.
OpenObserve
Rust-based, columnar, object-storage-backed. Claims 140x lower storage cost than Elasticsearch for logs.
Robusta
Kubernetes-native observability that turns Prometheus alerts into actionable, context-enriched events with auto-remediation playbooks.
SigNoz
Full-stack, OpenTelemetry-native APM + logs + metrics. The closest single-tool Datadog alternative.
Uptrace
OpenTelemetry APM backed by ClickHouse. Lean alternative to SigNoz.
Zabbix
Classic agent-based monitoring suite for hosts, networks, and services. Pre-Prometheus old guard, still actively developed.