Langfuse vs Phoenix (Arize)
Both are alternatives to LangSmith. Here's how they stack up — verified facts, no spin.
Also searched as Phoenix (Arize) vs Langfuse — same comparison, one verdict.
Langfuse
TOP PICKThe self-hosted default for LLM tracing — MIT core, framework-agnostic.
Langfuse is the most widely adopted open LLM observability platform: tracing, evaluation, prompt management and cost tracking, deployable with Docker on your own infrastructure so traces containing customer data never leave your network. It is deliberately framework-agnostic — LangChain, LlamaIndex, the provider SDKs directly, or OpenTelemetry — which makes it the natural exit from a LangChain-shaped tool. At 32k stars with commits landing daily it is the healthiest project in this category. Licensing needs precision: the core is MIT Expat, while the ee/ directories carry a separate enterprise licence.
Phoenix (Arize)
Strong evaluation tooling — but read the licence before you build on it.
Phoenix is Arize's tracing and evaluation tool, and its evaluation workflow is among the best available: run experiments, score outputs against datasets, and inspect where a chain went wrong. It runs locally in a notebook or as a self-hosted service. The critical detail most listicles omit is the licence — Phoenix is Elastic License 2.0, which is source-available rather than open source. You may use and modify it, but you may not offer it to third parties as a hosted or managed service, and you may not circumvent its licence-key functionality.
Side by side
| Langfuse | Phoenix (Arize) | |
|---|---|---|
| Sovereignty Score | 90 | 62 |
| Open source | Yes | No |
| Self-hostable | Yes | Yes |
| Local-first | Yes | Yes |
| License | MIT Expat (core); ee/ directories under a separate enterprise licence | Elastic License 2.0 (source-available, not OSI open source) |
| Pricing | Free to self-host — Docker Compose or Kubernetes, costs are your own infrastructure. A managed cloud with a free tier and paid plans exists if you would rather not run it. | Free to self-host under ELv2 for your own internal use. Arize's commercial platform is priced separately. |
Langfuse is Macrostack's recommended LangSmith alternative, so it's our pick here.
Langfuse
Strengths
- +Self-hosted: prompts and completions stay inside your network
- +Framework-agnostic — not tied to any one orchestration library
- +Tracing, evals, prompt management and cost tracking in one tool
- +32k stars and daily commits — the most active project in this category
Trade-offs
- −Self-hosting means running Postgres, ClickHouse and the collector yourself
- −The MIT core stops at the ee/ directories; SSO and some enterprise features sit behind a separate licence
- −Evaluation tooling is less polished than LangSmith's if you live inside LangChain
- −Trace storage grows fast — retention policy is your problem to plan
Phoenix (Arize)
Strengths
- +Excellent evaluation and experiment tooling — the strongest of this group
- +Runs locally, including straight from a notebook
- +Self-hostable, so traces stay in your infrastructure
- +Actively developed, with commits landing daily
Trade-offs
- −Elastic License 2.0 — source-available, NOT open source; you cannot offer it as a managed service
- −The licence restriction is a real constraint if your product is itself a platform
- −Score of 62 reflects the licensing limitation, not the engineering quality
- −Smaller community than Langfuse
Related alternative guides
Facts verified 2026-07-30. Licenses and pricing change — spotted something out of date? That's a correction we want.