Tired of the Datadog tax? Here are the best open-source APM tools — SigNoz, Sentry, Prometheus, and GlitchTip — that give you full observability without vendor lock-in. We break down their strengths, OpenTelemetry support, and which team size each fits best.
If you've ever looked at a Datadog invoice and felt a little sick, you're not alone. The "Datadog tax" is real — per-host pricing, per-event surcharges, and surprise line items that make observability one of the fastest-growing costs on any engineering budget.
The antidote? Open-source APM tools that you can self-host, audit, and extend. The ecosystem has matured fast, especially with OpenTelemetry becoming the universal data standard. Here are the tools worth your time.
SigNoz is the closest thing to a drop-in open-source replacement for Datadog. It ingests metrics, traces, and logs into a single UI, all powered by OpenTelemetry-native instrumentation.1
What makes it stand out: you don't need separate tools for metrics (Prometheus), traces (Jaeger), and logs (Elasticsearch). SigNoz handles all three in one backend, with a query builder that feels familiar if you've used Datadog's interface.
Best for: teams that want a single pane of glass for observability and are willing to run a moderately complex self-hosted stack (ClickHouse + query service). If you're already instrumenting with OpenTelemetry, SigNoz is the most natural fit.
Sentry has been the gold standard for error tracking for years, and its open-source core (the self-hosted version) is remarkably capable.2 It catches exceptions, groups them intelligently, and surfaces performance data alongside stack traces.
Sentry's bread and butter is developer-facing error monitoring — it tells you what broke, where, and how many users were affected. The performance monitoring features (spans, transaction traces) have improved significantly, though they're not as deep as dedicated tracing tools.
Best for: teams that prioritize error tracking and crash reporting above all else. If your biggest pain point is "we don't know when production breaks," Sentry is the right answer. It's also the easiest to set up of the four tools here.
Prometheus is the CNCF-graduated industry standard for metrics collection and alerting.3 It scrapes time-series data from your services, stores it efficiently, and powers alerting rules that have kept Kubernetes clusters running for years.
Prometheus doesn't do traces or logs — it's metrics-only by design. But what it does, it does exceptionally well. The PromQL query language is powerful, the alertmanager ecosystem is battle-tested, and the export format has become the lingua franca of infrastructure monitoring.
Best for: Kubernetes-native teams and anyone who needs rock-solid metrics and alerting. If you're on K8s, Prometheus is almost certainly already in your stack. Pair it with Grafana for dashboards and Loki for logs, and you have a complete (if multi-tool) observability pipeline.
GlitchTip is an open-source error tracking and uptime monitoring tool that positions itself as a simpler alternative to Sentry.4 It's built on the same event schema (Sentry SDKs are compatible), but with a much smaller resource footprint.
Where Sentry can feel heavy — especially the self-hosted version — GlitchTip runs on a single server with PostgreSQL and Redis. It handles error grouping, release tracking, and basic uptime checks without the overhead.
Best for: small teams, side projects, and anyone who wants error tracking without the operational burden. If Sentry feels like overkill for your scale, GlitchTip is a smart middle ground.
| Tool | Primary focus | OpenTelemetry support | Self-hosting complexity |
|---|---|---|---|
| SigNoz | Metrics + Traces + Logs | Native (OTel-native) | Medium (ClickHouse backend) |
| Sentry | Errors + Performance | Via SDK bridge | Medium-High (many services) |
| Prometheus | Metrics only | Via OTel collector | Low (single binary) |
| GlitchTip | Errors + Uptime | Compatible via Sentry SDKs | Low (single server) |
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All tools listed are open-source and can be self-hosted. Pricing mentioned refers to their cloud/SaaS tiers where applicable.
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