#1 ranked
LangfuseOpen-source LLM observability and evaluation
Free plan
Open source with nearly all features MIT-licensed
Self-host the full product free, no seat or usage caps
Best AI tools
Best AI LLM Observability in 2026
A hands-on look at the top ai llm observability tools — features, pricing, and who each is best for. Every tool hand-reviewed and ranked by real usefulness, no pay-to-play.
Top ranked ai llm observability
Rank
Tool
Pricing
Rating
Action
Compare the best ai llm observability
Each card links to full details and alternatives.
#2 ranked
HeliconeOpen-source LLM observability and AI gateway in one line of code.
Free plan
Extremely easy integration via a one-line base-URL swap
Open source under Apache 2.0 and free to self-host
#3 ranked
BraintrustEval-first evaluation and observability platform for AI applications.
Free plan
Deep, eval-first feature set with scorers, experiments, and statistical rigor
Strong CI/CD integration to catch regressions before deploy
#4 ranked
VellumBuild, evaluate, and deploy LLM apps and agents with confidence.
Free plan
Combines prompt, workflow, evaluation, and deployment in one platform
Visual workflow builder lowers the barrier for cross-functional collaborators
#5 ranked
PortkeyOpen-source AI gateway and control plane for production Gen AI.
Free plan
Fully open-source, self-hostable gateway for data control and no lock-in
Access to more than 1,600 models through one API
#6 ranked
TraceloopOpen-source LLM observability built on OpenTelemetry
Free plan
Built on open standard OpenTelemetry, avoiding lock-in
Open-source OpenLLMetry library is free (Apache-2.0)
#7 ranked
Arize PhoenixOpen-source LLM and agent observability built on OpenTelemetry.
Free plan
Free and source-available, self-hosts in one command
Built on open OpenTelemetry standards
#8 ranked
OpikOpen-source LLM evaluation, tracing, and observability by Comet.
Free plan
Full platform is Apache-2.0 and free to self-host
Combines tracing and evaluation in one tool
#9 ranked
DeepEvalOpen-source LLM evaluation framework with pytest-style testing.
Free plan
pytest-style workflow fits developer habits
50+ research-backed metrics out of the box
#10 ranked
RagasOpen-source evaluation toolkit for RAG and LLM applications.
Free
Focused, research-backed RAG metrics
Free and open source
FAQ
What is the best ai llm observability tool?
Langfuse leads our current pick for this category. The best choice depends on your needs — compare features, pricing, and fit below.
How are these tools ranked?
Today this list is editorially curated for category fit. As tools gather community engagement, rankings will also weigh views, votes, and reviews.
Are free tools included?
Yes. Free, freemium, paid, and contact-sales tools can appear if they are published in this category.