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
Role Observability Observability
Tags observability, evaluation, persona-data-scientist, persona-platform-engineer observability, evaluation, prompt-management, persona-data-scientist, persona-platform-engineer
License Elastic-2.0 MIT
Open source Yes Yes
Self-hostable Yes Yes
MCP support No No
Pricing free freemium
Price Free tier Free tier
Usage cost No model cost No model cost
Models multi multi
Languages python, typescript python, typescript
GitHub stars 10.4k 30.4k
Last activity 2026-07-04 2026-07-03