Langfuse
The best-known open source LLM observability platform, now owned by ClickHouse.
- MIT core plus a separate enterprise licence over ee/, web/src/ee/ and worker/src/ee/
- 33,900+ GitHub stars, acquired by ClickHouse in January 2026
- Hobby free with 50,000 units/month, Core $29, Pro $199, Enterprise $2,499/month
- Mature prompt management and a well documented OpenTelemetry path
Best for: Teams who want the largest community, the most integrations and the most mature prompt tooling.
Watch out: Nine features need a licence key when self-hosting, including audit logs, data retention policies and server-side data masking. Those are exactly what a regulated team self-hosts for.
Full Langfuse comparisonOpik
Comet ML's observability and evaluation platform, with the largest community of the clean-licence options.
- Apache-2.0 with no enterprise directory, 21,697 GitHub stars (August 2026)
- Self-hosted build has all features except user management
- Free Cloud at $0, Pro Cloud $19/month, Enterprise custom
- First-party OpenTelemetry support
Best for: Teams who want a complete self-hosted build with a genuinely clean licence and a large community behind it.
Watch out: Five datastores to operate: MySQL, Redis, ClickHouse, Zookeeper and MinIO. Whether it maps gen_ai.* semantic conventions or a proprietary schema was not something we could confirm from its docs.
OpenLIT
The lightest option here: SDK to OpenTelemetry Collector to ClickHouse, and nothing else.
- Apache-2.0, 2,731 GitHub stars (August 2026)
- One datastore
- No paid tier exists today
- Maintains the gen_ai semantic conventions with the OpenTelemetry community
Best for: Teams optimising for the least infrastructure to operate, who will self-host permanently.
Watch out: No managed cloud. OpenLIT Cloud is listed as coming soon with no pricing, so there is nowhere to go if you later need a hosted product with an SLA.
Laminar
An Apache-2.0 platform where the cloud and self-hosted builds have feature parity.
- Apache-2.0 (in LICENSE.md rather than LICENSE), 3,212 GitHub stars (August 2026)
- PostgreSQL, ClickHouse and Quickwit: three datastores
- Free $0 with 1 GB, Starter $30, Pro $150/month, Enterprise custom
- Accepts OTLP over gRPC, HTTP protobuf and HTTP JSON
Best for: Teams who want the option to move between cloud and self-hosted without losing features.
Watch out: The smallest community here, and a recent rebrand has left some redirecting documentation URLs.
OpenLLMetry
Instrumentation rather than a platform: it produces spans and sends them to a backend you already run.
- Apache-2.0, 7,409 GitHub stars (August 2026)
- Its semantic conventions became the basis for OpenTelemetry's official GenAI effort
- Exports to Traceloop or 30+ external backends including Datadog, Grafana and Honeycomb
- Traceloop platform: free tier with 24 hour retention, then Enterprise
Best for: Teams who already operate an observability stack and would rather have LLM spans inside it than beside it.
Watch out: It is not a backend. You still need somewhere for the spans to land. Traceloop's free tier retains data for 24 hours, which is a demo rather than a production tier.
Everstack
Observability that arrives as a side effect of routing, on a control plane that also runs agents and sandboxes.
- Apache-2.0 across the repository, no enterprise directory
- Self-hosting is the default at any tier
- Traces exist without instrumenting each service, because requests pass through the gateway
- Starter $0, Build $20/month, Scale $100/month (August 2026)
Best for: Teams with services in several languages, or integrations they cannot instrument, where per-service rollout is the thing blocking coverage.
Watch out: A much smaller community than Langfuse or Opik, and a younger trace UI. If observability is your only problem, the focused tools are more polished.