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, Langfuse, Promptfoo, W&B Weave, Ollama. None of them are paid-only.

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.

9 Braintrust alternatives (9 free)

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.

Tool	Braintrust (you searched)	Arize Phoenix	Langfuse	Promptfoo
Pricing	freemium	free	freemium	freemium
Best for	Free Starter plan ships model credits and scored evals with no card required	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	Open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI
Visit	Open ↗	Open ↗	Open ↗	Open ↗

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

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

Visit

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

Visit