Category
LLM Observability
See what your LLM app is really doing.
10 tools·10 with free plan·2 with free trial
Read the editor's roundup →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
Open-source LLM and agent observability built on OpenTelemetry.
#observability#llm-evaluation#open-source#tracing
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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?
- 10 tools in this category offer a free plan. Another 2 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.