Best free Braintrust alternatives

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

ToolBraintrust (you searched)Arize PhoenixGoogle StaxLaminar
Pricingfreemiumfreefreefree
Best forFree Starter plan ships model credits and scored evals with no card requiredFully 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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Braintrust alternatives — straight answers

What is the best free alternative to Braintrust?

Arize Phoenix is the closest free alternative to Braintrust: 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 Braintrust alternatives?

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

Is Braintrust free?

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

How were these Braintrust 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 Braintrust alternatives

Browse LLM Eval & Observability →

Arize Phoenix

LLM Eval & Observability
free

✦ WhyA Braintrust 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 Braintrust 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
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Laminar

LLM Eval & Observability
freeNew

✦ WhyA Braintrust 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 Braintrust 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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Promptfoo

LLM Eval & Observability
freemium

✦ WhyA Braintrust 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
Visit

W&B Weave

LLM Eval & Observability
freemium

✦ WhyA Braintrust 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 Braintrust 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 Braintrust 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 Braintrust 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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Braintrust head-to-head

Braintrust vs Arize PhoenixBraintrust vs Google StaxBraintrust vs LaminarBraintrust vs LangfuseBraintrust vs PromptfooBraintrust vs W&B WeaveBraintrust vs Opik (Comet)Braintrust vs LangSmith