Arize Phoenix vs Promptfoo

Arize Phoenix is free, with no paid plan attached. Promptfoo is freemium — a usable free tier with paid plans above it. Both are listed under LLM Eval & Observability, so this is a like-for-like comparison. Neither is ranked above the other — Flocci carries no sponsored placement.

Arize Phoenix vs Promptfoo — straight answers

Arize Phoenix vs Promptfoo: what is the difference?

Arize Phoenix is free, with no paid plan attached and is listed for fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported). Promptfoo is freemium — a usable free tier with paid plans above it and is listed for open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI. Both sit in LLM Eval & Observability.

Is Arize Phoenix or Promptfoo cheaper to start with?

Arize Phoenix is the cheaper starting point: it is free, with no paid plan attached, while Promptfoo is freemium — a usable free tier with paid plans above it. Pricing tiers here come from the catalog, not from a promotional page.

Which should I choose, Arize Phoenix or Promptfoo?

Choose Arize Phoenix if you need fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported); choose Promptfoo if you need open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI. Flocci AI Tools does not rank one above the other — it shows both feature sets side by side and lets the requirement decide.

Arize Phoenix compared with Promptfoo: pricing tier, category, listed capabilities and links.
 Arize PhoenixPromptfoo
Pricing tierFreeFree tier + paid plans
Free to startYesYes
CategoryAI Models & Local ExecutionAI Models & Local Execution
TypeLLM Eval & ObservabilityLLM Eval & Observability
Listed capabilities
  • Fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported)
  • Combines tracing, evals, datasets, experiments and prompt playground in one local-first tool
  • AI engineering agent (PXI) built in for automated troubleshooting of traces
  • Open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI
  • Automated red-teaming to surface prompt injection, jailbreak and data-leak vulnerabilities
  • 300,000+ user community with an enterprise tier for teams needing hosted guardrails
Tagsarize phoenix, llm observability open source, tracing, evaluation, rag debugging, freepromptfoo, prompt testing, llm red teaming, eval framework, open source, free, ci for prompts
Websitephoenix.arize.compromptfoo.dev
Full pageArize Phoenix details →Promptfoo details →
AlternativesArize Phoenix alternatives →Promptfoo alternatives →

Also worth comparing

All LLM Eval & Observability →

Braintrust

LLM Eval & Observability
freemium
  • Free Starter plan ships model credits and scored evals with no card required
  • Unlimited users/projects/datasets/playgrounds even on the free tier
  • Built-in playground for side-by-side prompt/model comparison against production traces
Visit

Langfuse

LLM Eval & Observability
freemium
  • Fully open-source and self-hostable for free via Docker Compose/Kubernetes, not just a hosted SaaS
  • Hobby cloud plan is free with no credit card, 50k observability units/month
  • Combines tracing, prompt management, evals and datasets in one open platform
Visit

W&B Weave

LLM Eval & Observability
freemium
  • Agent-native tracing model with sessions, steps, tools and sub-agents as first-class concepts (not generic spans)
  • Pre-built safety/quality scorers for toxicity, bias, PII and hallucination detection out of the box
  • Built on Weights & Biases' existing ML-experiment infrastructure, useful for teams already on W&B
Visit