A agentindex
Comparison

Arize Phoenix vs Langfuse

A like-for-like, spec-level comparison. Both entries are verified against their docs and repo.

Arize Phoenix

Open-source LLM tracing and eval.

  • + Open source with OTel foundations
  • + Good LLM-as-a-judge evals built in
  • − Elastic license restricts some hosted offerings
  • − Enterprise features in the paid Arize cloud

Langfuse

The most-used open-source LLM observability tool.

  • + Open source and self-hostable
  • + Framework-agnostic via OpenTelemetry
  • − Self-hosting ClickHouse is operational work
  • − Eval features trail dedicated eval tools
Spec Arize Phoenix Langfuse
Category eval-observability eval-observability
License Elastic-2.0 MIT
Open source Yes Yes
Self-hostable Yes Yes
MCP support No No
Pricing free freemium
Starting price Self-host free Self-host free; cloud tier
Models multi multi
Languages python, typescript python, typescript
GitHub stars 10.3k 29.8k
Last activity 2026-06-25 2026-06-25