Arize Phoenix vs promptfoo
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.
Open source · MIT
CLI and library for testing LLM prompts and red-teaming AI apps, with declarative configs.
The short answer
Choose Arize Phoenix if you need…
- Local debugging of LLM traces
- OpenTelemetry-based stacks
Choose promptfoo if you need…
- Developers building apps on top of LLM APIs who want repeatable prompt tests
- Teams comparing several models side by side on the same prompts
- People who want to run automated LLM checks in CI/CD pipelines
- Teams looking for a local, command-line way to scan LLM apps for security issues
Side-by-side
| Arize Phoenix | promptfoo | |
|---|---|---|
| Type | Prompting · Evaluation & observability | Dev tool |
| Price | Open source | Free and open source |
| Licence | — | MIT |
| GitHub stars | — | 26.7k |
| Setup difficulty | — | Intermediate |
| How you get it | — | Install with a package manager |
| Platforms | Self-hosted, Web, API | CLI, Web |
| Works with | LangChain, LlamaIndex, OpenAI | GitHub, OpenAI, Anthropic |
| Main language | — | TypeScript |
| Last code update | — | 4 days ago |
| Hands-on tested by us | Not yet | — |
| Last checked | 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.
promptfoo
Promptfoo is a command-line tool and library for evaluating LLM-based apps. You write a declarative config listing prompts, models, and test cases, then run it to compare outputs across providers such as OpenAI, Anthropic, and Ollama. It also includes red-teaming features that scan AI apps for security vulnerabilities.
Best for
Arize Phoenix
- Local debugging of LLM traces
- OpenTelemetry-based stacks
promptfoo
- Developers building apps on top of LLM APIs who want repeatable prompt tests
- Teams comparing several models side by side on the same prompts
- People who want to run automated LLM checks in CI/CD pipelines
- Teams looking for a local, command-line way to scan LLM apps for security issues
Strengths
Arize Phoenix
- OpenTelemetry tracing
- LLM-as-judge evals
- Prompt playground
- Datasets and experiments
promptfoo
- The README states that evals run locally and prompts never leave your machine
- Works with many providers and any LLM API, according to the README
- Has a large community with about 26,500 stars and an MIT license
Not ideal for
Arize Phoenix
—
promptfoo
- People who want a no-code, point-and-click tool, since the workflow centers on the command line and config files
- Projects that do not call any LLM APIs, because there is nothing for it to evaluate
- Anyone who needs a guaranteed security audit, since the README describes scanning as a tool rather than a complete assurance
Trade-offs
Arize Phoenix
—
promptfoo
- The README says the project is now part of OpenAI, which may matter to some users evaluating independence
- Requires API keys for most providers, which means usage costs from those providers
- Some claims in the README, such as usage by OpenAI and Anthropic and serving 10M+ users, are not independently verified here
Getting started
Arize Phoenix
Get started on the Arize Phoenix websitepromptfoo
Install globally with npm
npm install -g promptfooCreate a starter example
promptfoo init --example getting-startedFrequently asked questions
What is the difference between Arize Phoenix and promptfoo?
Arize Phoenix: An open-source tool for tracing, evaluating and experimenting with LLM and agent applications, built on OpenTelemetry. promptfoo: CLI and library for testing LLM prompts and red-teaming AI apps, with declarative configs. Arize Phoenix suits local debugging of llm traces, while promptfoo suits developers building apps on top of llm apis who want repeatable prompt tests.
Are Arize Phoenix and promptfoo free?
Arize Phoenix: Open source. promptfoo: Free and open source.
What are other alternatives to Arize Phoenix and promptfoo?
Other options people compare them with include Langfuse, Confident AI (DeepEval), LangSmith, Opik, 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.