Arize Phoenix vs LangSmith
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
AI tool · Open source
An open-source tool for tracing, evaluating and experimenting with LLM and agent applications, built on OpenTelemetry.
AI tool · Freemium
LangChain's platform for tracing, evaluating and monitoring LLM apps, with a prompt hub and playground.
The short answer
Choose Arize Phoenix if you need…
- Local debugging of LLM traces
- OpenTelemetry-based stacks
Choose LangSmith if you need…
- LangChain and LangGraph users
- Dataset-based evaluation
Side-by-side
| Arize Phoenix | LangSmith | |
|---|---|---|
| Type | Prompting · Evaluation & observability | Prompting · Evaluation & observability |
| Price | Open source | Freemium |
| Platforms | Self-hosted, Web, API | Web, API |
| Works with | LangChain, LlamaIndex, OpenAI | LangChain, OpenAI |
| Hands-on tested by us | Not yet | Not yet |
| Last checked | 2026-10-29 | 2026-10-29 |
What each one is
Arize Phoenix
An open-source tool for tracing, evaluating and experimenting with LLM and agent applications, built on OpenTelemetry. Standards-based and free to run locally. Enterprise features live in Arize's paid platform.
LangSmith
LangChain's platform for tracing, evaluating and monitoring LLM apps, with a prompt hub and playground. Deep tooling, especially inside the LangChain ecosystem. Less compelling if you don't use LangChain.
Best for
Arize Phoenix
- Local debugging of LLM traces
- OpenTelemetry-based stacks
LangSmith
- LangChain and LangGraph users
- Dataset-based evaluation
Strengths
Arize Phoenix
- OpenTelemetry tracing
- LLM-as-judge evals
- Prompt playground
- Datasets and experiments
LangSmith
- Detailed run traces
- Datasets and evaluators
- Prompt hub and playground
- Production monitoring
Frequently asked questions
What is the difference between Arize Phoenix and LangSmith?
Arize Phoenix: An open-source tool for tracing, evaluating and experimenting with LLM and agent applications, built on OpenTelemetry. LangSmith: LangChain's platform for tracing, evaluating and monitoring LLM apps, with a prompt hub and playground. Arize Phoenix suits local debugging of llm traces, while LangSmith suits langchain and langgraph users.
Are Arize Phoenix and LangSmith free?
Arize Phoenix: Open source. LangSmith: Freemium.
What are other alternatives to Arize Phoenix and LangSmith?
Other options people compare them with include Langfuse, Confident AI (DeepEval), Opik, promptfoo, Braintrust.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.