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LLM Observability

See what your LLM app is really doing.

21 tools·20 with free plan·11 with free trial

Read the editor's roundup →

Trace, monitor, and evaluate LLM apps — logging, cost tracking, and quality evals (LLMOps).

21 tools reviewed20 with a free plan11 with a free trial21 with an API19 self-hostable

Top picks

01

Open-source LLM observability and evaluation

Langfuse is our top recommendation for teams that want LLM observability without vendor lock-in. Moving essentially the entire product to MIT was a rare, genuinely developer-friendly move: you can self-host the full feature set for free, with no seat or usage caps. The tracing, prompt management, and evaluation tooling are solid and framework-agnostic, so it fits whether or not you use LangChain. The ClickHouse acquisition looks like a stable, aligned home. If open source and self-hosting matter, start here.

freemium·Free self-hosted / cloud tier; Core from $29/month

02

Open-source LLM observability and AI gateway in one line of code.

Helicone is one of the easiest ways to add LLM logging and a gateway, and the open-source, self-hostable version is genuinely appealing and free. The critical caveat is that after the March 2026 Mintlify acquisition, the product is in maintenance mode with no roadmap or new features. For a self-hosted logging layer it can still work well, but weigh the frozen roadmap and possible migration before making a new long-term production commitment.

freemium·$79/mo

03

Eval-first evaluation and observability platform for AI applications.

Braintrust is a serious, well-funded choice for teams that want to make evaluation systematic and wire it into CI/CD. The eval tooling, playground, and production-traces-to-dataset loop are genuinely strong. Trade-offs: it is not open source, self-hosting is Enterprise-only, and pricing jumps from free to $249 per month with many controls like SSO and RBAC behind Enterprise. Data- and score-based billing also makes costs less predictable at volume.

freemium·$249/mo

All LLM Observability

Build, evaluate, and deploy LLM apps and agents with confidence.

#llmops#ai-agents#prompt-engineering#evaluation

Open-source AI gateway and control plane for production Gen AI.

#ai-gateway#llmops#open-source#observability 2 views

Open-source LLM observability built on OpenTelemetry

#llm observability#monitoring#opentelemetry#developer tools 1 views

Open-source LLM and agent observability built on OpenTelemetry.

#observability#llm-evaluation#open-source#tracing 1 views

Open-source LLM evaluation, tracing, and observability by Comet.

#llm-evaluation#observability#open-source#tracing 1 views

Open-source LLM evaluation framework with pytest-style testing.

#llm-evaluation#testing#open-source#rag 1 views

Open-source evaluation toolkit for RAG and LLM applications.

#rag#llm-evaluation#open-source#testing 1 views

Open-source, OpenTelemetry-based observability for LLM applications

#llm-observability#opentelemetry#tracing#evaluations

Prompt management, versioning, and observability workspace for non-technical teams

#prompt-management#llm-observability#prompt-versioning#evaluation

Open-source LLM observability and prompt management for chatbots and RAG

#llm-observability#open-source#tracing#prompt-management 1 views

Observability and evaluation platform for AI agents and LLM applications

#llm-observability#evaluation#tracing#agent-monitoring 1 views

Evaluation intelligence and observability platform for GenAI apps and agents

#llm-evaluation#observability#guardrails#genai-metrics

Open-source, OpenTelemetry-native observability and evals built for AI agents

#llm-observability#agent-tracing#opentelemetry#evals 1 views

Unified AI evaluation, observability, and governance for regulated enterprises

#llm-observability#ai-evaluation#ai-governance#compliance 1 views

Observability, evaluation, and experimentation platform for LLM teams

#llm-observability#evaluation#monitoring#tracing 1 views

End-to-end evaluation and observability for AI agents and LLM apps

#llm-observability#evaluation#agent-simulation#tracing

LLM experimentation, evaluation and human annotation for small teams

#llm-evaluation#experiment-tracking#human-annotation#prompt-playground

OpenTelemetry-native observability for LLM calls, tools, and agent handoffs

#opentelemetry#llm tracing#agent observability#token cost

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Frequently asked questions

What's the best llm observability tool?: Langfuse currently leads in community votes. Langfuse is our top recommendation for teams that want LLM observability without vendor lock-in. Moving essentially the entire product to MIT was a rare, genuinely developer-friendly move: you can self-host the full feature set for free, with no seat or usage caps. The tracing, prompt management, and evaluation tooling are solid and framework-agnostic, so it fits whether or not you use LangChain. The ClickHouse acquisition looks like a stable, aligned home. If open source and self-hosting matter, start here.
Are there free options?: 20 tools in this category offer a free plan. Another 11 have a free trial.
How do you rank these tools?: Tools are ranked by a combination of community upvotes, editorial review, and feature breadth. Our editors review pricing and capabilities quarterly.
Can I suggest a tool we're missing?: Yes — submit it here. Our team reviews submissions weekly.