Arize Phoenix vs Braintrust
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
An evaluation and observability platform for scoring prompts and models against datasets and monitoring production.
The short answer
Choose Arize Phoenix if you need…
- Local debugging of LLM traces
- OpenTelemetry-based stacks
Choose Braintrust if you need…
- Systematic evals before shipping
- Comparing prompt versions with scores
Side-by-side
| Arize Phoenix | Braintrust | |
|---|---|---|
| Type | Prompting · Evaluation & observability | Prompting · Evaluation & observability |
| Price | Open source | Freemium |
| Platforms | Self-hosted, Web, API | Web, API |
| Works with | LangChain, LlamaIndex, OpenAI | OpenAI, Anthropic, Vercel |
| 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.
Braintrust
An evaluation and observability platform for scoring prompts and models against datasets and monitoring production. Fast, well-designed eval loop. Getting value means investing in good datasets and scorers.
Best for
Arize Phoenix
- Local debugging of LLM traces
- OpenTelemetry-based stacks
Braintrust
- Systematic evals before shipping
- Comparing prompt versions with scores
Strengths
Arize Phoenix
- OpenTelemetry tracing
- LLM-as-judge evals
- Prompt playground
- Datasets and experiments
Braintrust
- Experiments with scorers
- Prompt playground
- Logging and tracing
- Datasets
Frequently asked questions
What is the difference between Arize Phoenix and Braintrust?
Arize Phoenix: An open-source tool for tracing, evaluating and experimenting with LLM and agent applications, built on OpenTelemetry. Braintrust: An evaluation and observability platform for scoring prompts and models against datasets and monitoring production. Arize Phoenix suits local debugging of llm traces, while Braintrust suits systematic evals before shipping.
Are Arize Phoenix and Braintrust free?
Arize Phoenix: Open source. Braintrust: Freemium.
What are other alternatives to Arize Phoenix and Braintrust?
Other options people compare them with include Langfuse, Confident AI (DeepEval), LangSmith, Opik, promptfoo.
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.