LLM Eval & Observabilityfree

Arize Phoenix

Fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported)

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What Arize Phoenix does

  • 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

Arize Phoenix — straight answers

What is Arize Phoenix?

Arize Phoenix is listed under LLM Eval & Observability, in the AI Models & Local Execution category on Flocci AI Tools. Fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported). It is free, with no paid plan attached, and it lives at phoenix.arize.com.

Is Arize Phoenix free?

Arize Phoenix is listed as fully free — there is no paid tier attached to it in the catalog. That makes it one of the 115 entries on Flocci AI Tools with no upgrade path built in.

What can Arize Phoenix do?

Arize Phoenix does 3 things the catalog singles out: 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.

What is the best free alternative to Arize Phoenix?

Braintrust is the closest free alternative: it sits in the same LLM Eval & Observability sub-category and is free tier + paid plans. Langfuse, Promptfoo and W&B Weave also start free. The full list is on the alternatives page.

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Arize Phoenix alternatives

Compare all alternatives →

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
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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
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Promptfoo

LLM Eval & Observability
freemium
  • 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
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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
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Ollama

Local LLM Runners
free
  • The default way to run LLMs locally
  • One command to run Llama, Qwen, DeepSeek…
  • OpenAI-compatible local API
  • Free and open-source
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LM Studio

Local LLM Runners
free
  • Polished desktop GUI for local models
  • Discover, download and chat with GGUF models
  • Local server with OpenAI-compatible API
  • Free for personal use
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Head-to-head comparisons

Arize Phoenix vs LangfuseArize Phoenix vs BraintrustArize Phoenix vs PromptfooArize Phoenix vs W&B WeaveArize Phoenix vs OllamaArize Phoenix vs LM Studio