The de facto dashboard of observability: Grafana is the open-source frontend that turns the data stores you already run into interactive graphs. It does not store metrics itself; it connects to the data stores you already run and turns their contents into interactive dashboards. Supported sources number over 150 via plugins: Prometheus, Loki, Tempo, InfluxDB, Elasticsearch, MySQL, PostgreSQL, Microsoft SQL Server, AWS CloudWatch, Azure Monitor, Google Cloud Monitoring, and many more. Dashboards are built from a large library of panel types (time series, heatmaps, tables, gauges, logs) with template variables for reusable, parameterized views. Unified alerting evaluates rules against any connected data source, not just Prometheus, and routes notifications to Slack, PagerDuty, email, and other channels with grouping and silencing - unlike Prometheus Alertmanager, a single rule can combine a Loki log pattern, a PostgreSQL query result, and a CloudWatch metric. Dashboards serialize to JSON and data sources configure via provisioning files, so the entire observability setup can live in Git and deploy repeatably across environments. Explore mode adds ad-hoc querying outside dashboards, with split view for correlating a metric spike against the matching log lines, and access control spans organizations, teams, folder permissions, and OAuth, LDAP, and SAML integration. Written in Go and TypeScript, AGPL-licensed. Self-hosting gives you unlimited users, dashboards, and queries at flat hosting cost, without Grafana Cloud's usage-based pricing.

Sixty-thousand-plus GitHub stars make Uptime Kuma the most popular self-hosted monitoring tool - MIT-licensed, Node.js, and the standard replacement for UptimeRobot, Pingdom, and Freshping. It watches a dozen monitor types: HTTP(S) endpoints with keyword and JSON-query content validation, TCP ports, ICMP ping, DNS records, WebSockets, Docker containers via the socket, Steam game servers, MQTT brokers, gRPC services, and push-based heartbeats for cron jobs and internal workers. Checks run at intervals as tight as 20 seconds - versus UptimeRobot's 5-minute free tier - with unlimited monitors and unlimited data retention. When something fails, alerts fan out through 90+ notification channels: Slack, Discord, Telegram, email with LiquidJS templating, PagerDuty, OpsGenie, ntfy, Gotify, Matrix, and dozens more via native providers plus the Apprise library. Unlimited public or password-protected status pages - mappable to specific domains and organized into monitor groups - communicate health to customers, with maintenance windows that suppress alerts during planned work. The reactive dashboard graphs response times, tracks SSL certificate expiry with advance warnings, supports proxies and 2FA, and ships in dozens of languages. One Docker container with a SQLite volume covers an entire infrastructure.

One REST call, 130+ notification services: Apprise API wraps the well-known Apprise library in a lightweight Django/Gunicorn microservice, so "send an alert" works the same whether it goes to Slack, Discord, Telegram, Teams, email, SMS, Pushover, or PagerDuty - each addressed by a simple URL scheme. It solves the credential-sprawl problem cleanly: instead of embedding provider tokens in every app, cron job, and CI pipeline, you centralize them here and everything else just POSTs a body and title. Two modes cover every workflow. Stateless calls to /notify carry target URLs in the payload (or fall back to a default set via APPRISE_STATELESS_URLS); stateful mode stores named configurations server-side under keys, so /notify/{KEY} fans out to everything registered - with tag-based routing (comma for OR, space for AND) selecting which endpoints fire per message. Messages take info, success, warning, or failure types in text, Markdown, or HTML, with attachments up to a configurable size. A built-in web UI manages and tests configurations, APPRISE_CONFIG_LOCK makes the store read-only, service allow/deny lists restrict which schemes work, webhook remapping adapts third-party payloads, and a Prometheus /metrics endpoint watches the gateway itself.