Best free Promptfoo alternatives

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

ToolPromptfoo (you searched)Arize PhoenixGoogle StaxLaminar
Pricingfreemiumfreefreefree
Best forOpen-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CIFully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported)Build evals with human raters or LLM autoraters on your own dataOpen-source observability and evals platform for AI agents (Apache-2.0)
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Promptfoo alternatives — straight answers

What is the best free alternative to Promptfoo?

Arize Phoenix is the closest free alternative to Promptfoo: same LLM Eval & Observability sub-category, and it is free. Fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported)

Are there free Promptfoo alternatives?

Yes — 9 of the 9 alternatives listed here are free or freemium: Arize Phoenix, Google Stax, Laminar, Langfuse, Braintrust. None of them are paid-only.

Is Promptfoo free?

Promptfoo is free tier + paid. There is a free tier you can work in, with paid plans above it.

How were these Promptfoo 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.

All Promptfoo alternatives

Browse LLM Eval & Observability →

Arize Phoenix

LLM Eval & Observability
free

✦ WhyA Promptfoo alternative — Fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported).

  • 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
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Google Stax

LLM Eval & Observability
freeNew

✦ WhyA Promptfoo alternative — Build evals with human raters or LLM autoraters on your own data.

  • Build evals with human raters or LLM autoraters on your own data
  • Compare models and prompts on quality, latency and token cost
  • Prebuilt and custom evaluators
Visit

Laminar

LLM Eval & Observability
freeNew

✦ WhyA Promptfoo alternative — Open-source observability and evals platform for AI agents (Apache-2.0).

  • Open-source observability and evals platform for AI agents (Apache-2.0)
  • Traces, session replay for browser agents and evaluations
  • Self-hostable
Visit

Langfuse

LLM Eval & Observability
freemium

✦ WhyA Promptfoo 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 Promptfoo 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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W&B Weave

LLM Eval & Observability
freemium

✦ WhyA Promptfoo 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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Opik (Comet)

LLM Eval & Observability
freemiumNew

✦ WhyA Promptfoo alternative — Open-source LLM tracing, evaluation and prompt-optimization platform (Apache-2.0).

  • Open-source LLM tracing, evaluation and prompt-optimization platform (Apache-2.0)
  • Free cloud plan with 25k spans a month, up to 10 team members and 60-day retention
  • Self-host with no limits
Visit

LangSmith

LLM Eval & Observability
freemiumNew

✦ WhyA Promptfoo alternative — Tracing, evaluation datasets and prompt playground for LLM apps and agents.

  • Tracing, evaluation datasets and prompt playground for LLM apps and agents
  • Developer plan is free with 5k base traces a month and one seat
  • Framework-agnostic, works beyond LangChain
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DeepEval

LLM Eval & Observability
freeNew

✦ WhyA Promptfoo alternative — Open-source LLM evaluation framework with pytest-style tests and 50+ metrics.

  • Open-source LLM evaluation framework with pytest-style tests and 50+ metrics
  • RAG, agent and conversational metrics; red-teaming module
  • Apache-2.0; optional Confident AI cloud has a free tier
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Promptfoo head-to-head

Promptfoo vs Arize PhoenixPromptfoo vs Google StaxPromptfoo vs LaminarPromptfoo vs LangfusePromptfoo vs BraintrustPromptfoo vs W&B WeavePromptfoo vs Opik (Comet)Promptfoo vs LangSmith