# The best free LLM evaluation and observability tools Every option in the catalog for when you need to trace, score and debug what your AI app actually did — 12 LLM evaluation and observability tools, 12 of them free or freemium, with the pricing tier printed on every row. ## Stats - 12 tools listed - 12 free or freemium - 6 with no paid plan at all - 1 sub-categories covered ## FAQ ### What are the best free LLM evaluation and observability tools? Flocci AI Tools lists 12 of them, ordered free tiers first: Arize Phoenix, Google Stax, Laminar, DeepEval and EleutherAI LM Evaluation Harness. Every one of them is free or has a free tier. Each entry states what it uniquely does rather than a score. ### Which of these are completely free? 6 on this page are marked fully free with no paid plan at all: Arize Phoenix, Google Stax, Laminar, DeepEval and EleutherAI LM Evaluation Harness. The remaining 6 are freemium, trial or paid, and each is labelled with its exact tier so nothing surprises you at sign-up. ### How is this list ordered? Free tools first, then freemium, then trial, then paid, and alphabetically inside each tier. Nobody pays to appear higher: Flocci AI Tools carries no ads, no sponsored slots and no paid listings, so the order reflects price and nothing else. ## Quick picks ### Which LLM evaluation and observability tools work in a browser with no install? Arize Phoenix, Google Stax, Laminar, Braintrust and Langfuse all work in a browser tab with no install needed — just open the site and go. 9 of the 12 free LLM evaluation and observability tools listed here are browser-based. ### Which LLM evaluation and observability tools let you sign in with Google? Google Stax and Langfuse support Google sign-in, so you can start without creating a new account. That's 2 of the 12 free LLM evaluation and observability tools on this page. ### Which LLM evaluation and observability tools can you self-host or run offline? DeepEval, EleutherAI LM Evaluation Harness and OpenLLMetry (Traceloop) can be self-hosted or run locally without a browser — useful for privacy, air-gapped networks, or avoiding API rate limits. 3 of the 12 free LLM evaluation and observability tools here run offline. ## Tools - [Arize Phoenix](https://aitools.flocci.in/tool/arize-phoenix) — Free — Fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported) - [Google Stax](https://aitools.flocci.in/tool/google-stax) — Free — Build evals with human raters or LLM autoraters on your own data - [Laminar](https://aitools.flocci.in/tool/laminar) — Free — Open-source observability and evals platform for AI agents (Apache-2.0) - [DeepEval](https://aitools.flocci.in/tool/deepeval) — Free — Open-source LLM evaluation framework with pytest-style tests and 50+ metrics - [EleutherAI LM Evaluation Harness](https://aitools.flocci.in/tool/eleutherai-lm-evaluation-harness) — Free — Standard open framework for running hundreds of benchmarks (MMLU, GSM8K and more) against any LLM - [OpenLLMetry (Traceloop)](https://aitools.flocci.in/tool/openllmetry-traceloop) — Free — OpenTelemetry-based instrumentation for LLM calls, vector DBs and frameworks - [Braintrust](https://aitools.flocci.in/tool/braintrust) — Freemium — Free Starter plan ships model credits and scored evals with no card required - [Langfuse](https://aitools.flocci.in/tool/langfuse) — Freemium — Fully open-source and self-hostable for free via Docker Compose/Kubernetes, not just a hosted SaaS - [LangSmith](https://aitools.flocci.in/tool/langsmith) — Freemium — Tracing, evaluation datasets and prompt playground for LLM apps and agents - [Opik (Comet)](https://aitools.flocci.in/tool/opik-comet) — Freemium — Open-source LLM tracing, evaluation and prompt-optimization platform (Apache-2.0) - [Promptfoo](https://aitools.flocci.in/tool/promptfoo) — Freemium — Open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI - [W&B Weave](https://aitools.flocci.in/tool/w-b-weave) — Freemium — Agent-native tracing model with sessions, steps, tools and sub-agents as first-class concepts (not generic spans) --- Source: Flocci AI Tools — https://aitools.flocci.in/best/best-llm-eval-observability Facts last verified: October 2026