Datadog Synthetics bills per test run — one execution of one check from one location — so a single API check running every minute from three regions burns through 129,600 runs a month before a second monitor gets added, at $5 per 10,000 API runs or $12 per 1,000 browser runs. Checkly's Monitoring-as-Code plans compound this by metering check frequency, concurrency, and extra test locations separately, turning a 30-monitor setup into a four-figure monthly bill. Self-hosting this stack decouples cost from run count entirely: Gatus evaluates YAML-defined conditions and Monika chains multi-step HTTP probes across as many nodes and check intervals as the infrastructure allows. Cloudprober's Starlark scripting handles custom probe logic while exporting straight to an existing Prometheus or Datadog pipeline, and k6's k6/browser module runs Playwright-style scripted checks inside a Docker Compose stack with no per-run metering.
| Name | Main Category | Sub-Category | Target Alternative | Free Tier Summary | Self-Hostable? | Short Description | Primary Link |
|---|---|---|---|---|---|---|---|
Cloudprober | Product Analytics & Monitoring | Active Probing / Blackbox Monitoring | Datadog Synthetics / Google Cloud Uptime Checks | 100% Free - Self-Hosted (Apache-2.0) | Yes - Docker | Go binary that runs HTTP, PING, DNS, UDP, and gRPC probes plus custom Starlark scripts for complex multi-step checks, auto-discovering Kubernetes and GCP targets and exporting straight to Prometheus or Datadog. | |
Gatus | Product Analytics & Monitoring | Config-as-Code Health Checks & Status Pages | Better Stack / Atlassian Statuspage / Checkly / Datadog Synthetics | 100% Free - Self-Hosted (Apache 2.0 License) | Yes - Docker / Kubernetes | Developer-oriented Go binary that executes declarative HTTP, ICMP, TCP, DNS, gRPC, and SSH health checks defined in YAML. Evaluates responses against custom condition assertions (status codes, body patterns, latency thresholds) and automatically renders the results on a public status page while routing alerts to 25+ notification channels. | |
Monika | Product Analytics & Monitoring | CLI Synthetic Monitoring | Checkly / Datadog Synthetics | 100% Free - Self-Hosted (MIT) | Yes - Binary | Node.js CLI purpose-built for synthetic monitoring, using YAML-defined probes with request chaining to pass data between calls for multi-step API flow testing, alerting via Telegram, webhook, and more. | |
Statping-NG | Product Analytics & Monitoring | Status Page & Monitor Engine | Checkly / Datadog Synthetics (status page layer) | 100% Free - Self-Hosted (GPL-3.0) | Yes - Docker | Go-based monitor and public status page engine that checks HTTP, TCP, UDP, ICMP, and gRPC endpoints on configurable intervals and stores results in your own Postgres, MySQL, or SQLite database. | |
Grafana k6 | Product Analytics & Monitoring | Scripted API & Browser Test Automation | Checkly Browser Checks / Datadog Synthetic Browser Tests | 100% Free - Self-Hosted (AGPL-3.0) | Yes - Binary | JavaScript/TypeScript-scripted test engine whose k6/browser module runs Playwright-style multi-step browser and API checks on a schedule, exporting results to your own Prometheus, Grafana, or Datadog backend. |
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