What is the best free alternative to Arize Phoenix?

Langfuse is the closest free alternative to Arize Phoenix: same LLM Eval & Observability sub-category, and it is free tier + paid. Fully open-source and self-hostable for free via Docker Compose/Kubernetes, not just a hosted SaaS

Are there free Arize Phoenix alternatives?

Yes — 9 of the 9 alternatives listed here are free or freemium: Langfuse, Braintrust, Promptfoo, W&B Weave, Ollama. None of them are paid-only.

Is Arize Phoenix free?

Arize Phoenix is free. There is no paid plan attached to it in the catalog.

How were these Arize Phoenix alternatives chosen?

They are the other tools in LLM Eval & Observability, then the rest of AI Models & Local Execution, ordered free tiers first and capped at 9. There is no sponsorship and no paid placement in that ordering — only the pricing tier decides.

9 Arize Phoenix alternatives (9 free)

Looking for a free alternative to Arize Phoenix? Here are 9 llm eval & observability worth trying — 9 with a free tier. Arize Phoenix itself is free.

Tool	Arize Phoenix (you searched)	Langfuse	Braintrust	Promptfoo
Pricing	free	freemium	freemium	freemium
Best for	Fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported)	Fully open-source and self-hostable for free via Docker Compose/Kubernetes, not just a hosted SaaS	Free Starter plan ships model credits and scored evals with no card required	Open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI
Visit	Open ↗	Open ↗	Open ↗	Open ↗

Langfuse

LLM Eval & Observability

freemium

✦ WhyA Arize Phoenix alternative — Fully open-source and self-hostable for free via Docker Compose/Kubernetes, not just a hosted SaaS.

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

✦ WhyA Arize Phoenix alternative — Free Starter plan ships model credits and scored evals with no card required.

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

✦ WhyA Arize Phoenix alternative — Open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI.

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

✦ WhyA Arize Phoenix alternative — Agent-native tracing model with sessions, steps, tools and sub-agents as first-class concepts (not generic spans).

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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