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Best free LLM observability tools
Quick answer
Top pick by our maturity signal: Grafana Cloud AI Observability. Below are all 25 free or freemium pricing + in the observability category tools we track, ranked by the same objective GitHub-derived score. Maturity measures adoption and upkeep, not subjective quality — pick by your own constraints.
LLM observability tools with a free or freemium tier, ranked by our GitHub maturity signal. Ranking method is public — see methodology. Note: maturity reflects total GitHub adoption, so large general-purpose platforms (e.g. Grafana, Sentry, PostHog) can rank high on the strength of their parent project even where their LLM-specific features are newer — read the flags and pick by your constraints. Listings are free and editorially independent; sponsorship never changes facts or ranking.
| # | Tool | Maturity | Pricing | Flags |
|---|---|---|---|---|
| 1 | Grafana Cloud AI Observability | 100/100 (Mature) | freemium | OSS, self-host, OTel-native |
| 2 | MLflow (Tracing & GenAI) | 100/100 (Mature) | free | OSS, self-host, OTel-native |
| 3 | Opik (Comet) | 100/100 (Mature) | freemium | OSS, self-host |
| 4 | Portkey | 100/100 (Mature) | freemium | OSS, self-host, OTel-native |
| 5 | TensorZero | 100/100 (Mature) | free | OSS, self-host, OTel-native |
| 6 | Traceloop (OpenLLMetry) | 98/100 (Mature) | freemium | OSS, self-host, OTel-native |
| 7 | Helicone | 97/100 (Mature) | freemium | OSS, self-host |
| 8 | Pydantic Logfire | 95/100 (Mature) | freemium | OSS, self-host, OTel-native |
| 9 | OpenLIT | 92/100 (Mature) | free | OSS, self-host, OTel-native |
| 10 | Sentry AI Agent Monitoring | 90/100 (Mature) | freemium | OSS, self-host, OTel-native |
| 11 | PostHog LLM Analytics | 90/100 (Mature) | freemium | OSS, self-host, OTel-native |
| 12 | Langfuse | 90/100 (Mature) | freemium | OSS, self-host, OTel-native |
| 13 | SigNoz | 90/100 (Mature) | freemium | OSS, self-host, OTel-native |
| 14 | Arize Phoenix | 90/100 (Mature) | free | OSS, self-host, OTel-native |
| 15 | W&B Weave | 87/100 (Mature) | freemium | OSS, self-host, OTel-native |
| 16 | Langtrace | 58/100 (Growing) | freemium | OSS, self-host, OTel-native |
| 17 | WhyLabs (whylogs/LangKit) | 57/100 (Growing) | free | OSS, self-host |
| 18 | Phospho | 52/100 (Growing) | freemium | OSS, self-host |
| 19 | Arize AX | — | freemium | self-host, OTel-native |
| 20 | HoneyHive | — | freemium | self-host, OTel-native |
| 21 | LangSmith | — | freemium | self-host, OTel-native |
| 22 | Lunary | — | freemium | OSS, self-host, OTel-native |
| 23 | New Relic AI Monitoring | — | freemium | OTel-native |
| 24 | Respan (formerly Keywords AI) | — | freemium | OTel-native |
| 25 | TrueFoundry | — | freemium | self-host, OTel-native |
Frequently asked questions
What is the best free LLM observability tools?
By our public maturity signal (GitHub stars + recency + license), Grafana Cloud AI Observability ranks highest among the 25 free or freemium pricing + in the observability category tools we track. Maturity reflects adoption and upkeep, not subjective quality.
How is this ranking decided?
Tools are ranked by a reproducible maturity score computed only from public GitHub signals (log of stars + last-commit recency + license). The formula is published on our methodology page; ranking is never sold.