Arize Phoenix
Partial infoOpen-source LLM tracing and evaluation, OpenTelemetry-native.
Phoenix is Arize's open-source observability tool for tracing and evaluating LLM and RAG applications, built on OpenTelemetry (OpenInference). It runs locally or self-hosted, with Arize's platform for production monitoring.
License
Open source (Elastic License 2.0)
Deployment
Self-hosted, Managed
Pricing
Phoenix is free/open-source; Arize AX is the paid managed platform.
SDKs / languages
Python, TypeScript
Strengths
- OpenTelemetry-native, vendor-neutral
- Strong RAG/eval tooling
- Runs locally for free
Limitations
- Prompt management is limited
- Production monitoring pushes to paid Arize
Alternatives
Braintrust
Eval-first platform for iterating on LLM quality.
Datadog LLM Observability
LLM tracing and monitoring inside the Datadog platform.
Helicone
Open-source LLM logging and monitoring via a proxy.
Langfuse
Open-source LLM observability, evals, and prompt management.
LangSmith
Tracing, evals, and prompt management from the LangChain team.
Opik
Open-source LLM evaluation and tracing from Comet.
Facts verified 19 July 2026. Neutral summary, not an endorsement; verify current details with the vendor.