Arize Phoenix vs Opik
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 · Open source
Comet's open-source platform for logging, evaluating and monitoring LLM apps, including prompt optimisation.
The short answer
Choose Arize Phoenix if you need…
- Local debugging of LLM traces
- OpenTelemetry-based stacks
Choose Opik if you need…
- Open-source tracing and evals
- Automated prompt optimisation
Side-by-side
| Arize Phoenix | Opik | |
|---|---|---|
| Type | Prompting · Evaluation & observability | Prompting · Evaluation & observability |
| Price | Open source | Open source |
| Platforms | Self-hosted, Web, API | Web, Self-hosted, 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.
Opik
Comet's open-source platform for logging, evaluating and monitoring LLM apps, including prompt optimisation. Generous open-source feature set. Younger than some rivals, so expect rough edges.
Best for
Arize Phoenix
- Local debugging of LLM traces
- OpenTelemetry-based stacks
Opik
- Open-source tracing and evals
- Automated prompt optimisation
Strengths
Arize Phoenix
- OpenTelemetry tracing
- LLM-as-judge evals
- Prompt playground
- Datasets and experiments
Opik
- Tracing and logging
- LLM-as-judge metrics
- Prompt library
- Agent optimiser
Frequently asked questions
What is the difference between Arize Phoenix and Opik?
Arize Phoenix: An open-source tool for tracing, evaluating and experimenting with LLM and agent applications, built on OpenTelemetry. Opik: Comet's open-source platform for logging, evaluating and monitoring LLM apps, including prompt optimisation. Arize Phoenix suits local debugging of llm traces, while Opik suits open-source tracing and evals.
Are Arize Phoenix and Opik free?
Arize Phoenix: Open source. Opik: Open source.
What are other alternatives to Arize Phoenix and Opik?
Other options people compare them with include Langfuse, Confident AI (DeepEval), LangSmith, 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.