Best LLM Observability Tools in 2026
Updated
In short: Evidently AI is ranked #1 of 26 as of 7 October 2026, ahead of W&B Weave and OpenLIT. The best-ranked option with a free plan is W&B Weave. The lowest first paid tier on this page is Respan (formerly Keywords AI) at $16.58/mo.
When you build or operate LLM-powered applications, observability criteria can help you compare how tools surface model and workflow activity. Look at agent tracing, LLM tracing, and retrieval tracing, then weigh LLM evaluations and prompt management against the oversight you need. Token cost tracking adds a cost-related comparison point; deployment options, free-plan availability, and paid-from pricing round out the criteria. Evidently AI, W&B Weave, and OpenLIT are among the entries, alongside Promptfoo and Giskard. Focus on which traces and evaluation features matter in your work, and compare the listed deployment and pricing details before choosing what to explore.
26 LLM observability tools ranked on what their makers publish — plans and prices, free tiers, platforms and the facts on their own pages.
21 of the 25 here have a free tier you can use, 0 have open-source code on record, and 0 have full bars: free, open, on most of your devices and documented.
| # | App | Signal | Free tier | Open code | Devices | From | Score |
|---|---|---|---|---|---|---|---|
| 1 | Evidently AIWeb · Windows · Mac · Linux · Self-hosted · API | Three bars | — | 4 of 6 | $80/mo | 6.7 | |
| 2 | W&B WeaveWeb · Windows · Mac · Linux · Self-hosted · API | Three bars | — | 4 of 6 | $60/mo | 6.7 | |
| 3 | OpenLITWeb · Windows · Mac · Linux · Self-hosted · API | Three bars | — | 4 of 6 | Free | 6.6 | |
| 4 | PromptfooWeb · Windows · Mac · Linux · Self-hosted · API | Three bars | — | 4 of 6 | Free | 6.6 | |
| 5 | GiskardWeb · Linux · Self-hosted · API | Two bars | — | 2 of 6 | Free | 6.5 | |
| 6 | LangWatchWeb · Linux · Self-hosted · API | Two bars | — | 2 of 6 | €29/mo | 6.5 | |
| 7 | OpikWeb · Linux · Self-hosted · API | Two bars | — | 2 of 6 | $19/mo | 6.5 | |
| 8 | Arize AXWeb · Self-hosted · API | Two bars | — | 1 of 6 | $50/mo | 6.4 | |
| 9 | Arize PhoenixWeb · Self-hosted · API | Two bars | — | 1 of 6 | Free | 6.4 | |
| 10 | BraintrustWeb · Self-hosted · API | Two bars | — | 1 of 6 | $249/mo | 6.4 | |
| 11 | Confident AIWeb · Self-hosted · API | Two bars | — | 1 of 6 | $200/mo | 6.4 | |
| 12 | Fiddler AIWeb · Self-hosted · API | Two bars | — | 1 of 6 | Free | 6.4 | |
| 13 | GalileoWeb · Self-hosted · API | Two bars | — | 1 of 6 | $100/mo | 6.4 | |
| 14 | HeliconeWeb · Self-hosted · API | Two bars | — | 1 of 6 | $79/mo | 6.4 | |
| 15 | HoneyHiveWeb · Self-hosted · API | Two bars | — | 1 of 6 | Free | 6.4 | |
| 16 | LaminarWeb · Self-hosted · API | Two bars | — | 1 of 6 | $30/mo | 6.4 | |
| 17 | LangfuseWeb · Self-hosted · API | Two bars | — | 1 of 6 | $29/mo | 6.4 | |
| 18 | LangSmithWeb · Self-hosted · API | Two bars | — | 1 of 6 | $39/mo | 6.4 | |
| 19 | Maxim AIWeb · Self-hosted · API | Two bars | — | 1 of 6 | $29/mo | 6.4 | |
| 20 | Parea AIWeb · Self-hosted · API | Two bars | — | 1 of 6 | $150/mo | 6.4 | |
| 21 | Respan (formerly Keywords AI)Web · Self-hosted · API | Two bars | — | 1 of 6 | $16.58/mo | 6.4 | |
| 22 | AgentOpsWeb · Self-hosted · API | One bar | — | — | 1 of 6 | $40/mo | 5.4 |
| 23 | RagasLinux · Self-hosted · API | One bar | — | — | 1 of 6 | — | 5.4 |
| 24 | OpenLLMetryNo platforms listed | No signal | — | — | 0 of 6 | — | 5.1 |
| 25 | LunaryWeb | One bar | — | — | 1 of 6 | — | 4.8 |
Compare all 25 in a table
| # | App | Score | Free plan | From | Free plan | Paid from | LLM tracing | LLM evaluations |
|---|---|---|---|---|---|---|---|---|
| 1 | Evidently AI | 6.7 | Free plan | $80/mo | Yes | — | Yes | Yes |
| 2 | W&B Weave | 6.7 | Free plan | $60/mo | Yes | 60 /mo | Yes | Yes |
| 3 | OpenLIT | 6.6 | Free plan | Free | Yes | — | Yes | Yes |
| 4 | Promptfoo | 6.6 | Free plan | Free | Yes | — | — | — |
| 5 | Giskard | 6.5 | Free plan | Free | Yes | — | — | — |
| 6 | LangWatch | 6.5 | Free plan | €29/mo | Yes | — | Yes | Yes |
| 7 | Opik | 6.5 | Free plan | $19/mo | Yes | 19 /mo | Yes | Yes |
| 8 | Arize AX | 6.4 | Free plan | $50/mo | Yes | 50 /mo | Yes | Yes |
| 9 | Arize Phoenix | 6.4 | Free plan | Free | Yes | — | Yes | Yes |
| 10 | Braintrust | 6.4 | Free plan | $249/mo | Yes | 249 /mo | — | — |
| 11 | Confident AI | 6.4 | Free plan | $200/mo | Yes | 200 /mo | — | — |
| 12 | Fiddler AI | 6.4 | Free plan | Free | Yes | — | Yes | Yes |
| 13 | Galileo | 6.4 | Free plan | $100/mo | Yes | 100 /mo | — | — |
| 14 | Helicone | 6.4 | Free plan | $79/mo | Yes | 79 /mo | Yes | Yes |
| 15 | HoneyHive | 6.4 | Free plan | Free | Yes | — | Yes | Yes |
| 16 | Laminar | 6.4 | Free plan | $30/mo | Yes | 30 /mo | Yes | Yes |
| 17 | Langfuse | 6.4 | Free plan | $29/mo | Yes | 29 /mo | Yes | Yes |
| 18 | LangSmith | 6.4 | Free plan | $39/mo | Yes | — | Yes | Yes |
| 19 | Maxim AI | 6.4 | Free plan | $29/mo | Yes | — | — | — |
| 20 | Parea AI | 6.4 | Free plan | $150/mo | Yes | — | — | — |
| 21 | Respan (formerly Keywords AI) | 6.4 | Free plan | $16.58/mo | Yes | 199 /mo | Yes | Yes |
| 22 | AgentOps | 5.4 | No | $40/mo | Yes | 40 /mo | Yes | — |
| 23 | Ragas | 5.4 | No | — | Yes | — | — | — |
| 24 | OpenLLMetry | 5.1 | No | — | Yes | — | Yes | — |
| 25 | Lunary | 4.8 | No | — | No | — | Yes | Yes |
Is your app on this list?
Numbered spots on this list can be sponsored, and a sponsored row is labelled as paid.
Questions about this list
Which LLM observability tool is ranked first on Freedom251?
Evidently AI is ranked #1 of 26 with a score of 6.7. W&B Weave is second and OpenLIT third.
How many of these have a free plan?
21 of the 25 on this page publish a free plan on their own pricing pages.
Which is the cheapest paid option?
On this page, Respan (formerly Keywords AI) has the lowest first paid tier we found: $16.58/mo.
How is this list ranked?
Ranked free-and-open first: a usable free tier and open-source code, then the platforms it runs on and its documentation.