Best LLM Observability Tools in 2026
Updated
In short: Arize AX is ranked #1 of 25 as of 2 October 2026, ahead of Langfuse and Opik. The best-ranked option with a free plan is Langfuse. The lowest first paid tier on this page is Opik at $19/mo.
When models power application features, observability tools help you follow their activity and inspect what happens across a workflow. Compare agent, LLM, and retrieval tracing with evaluation, prompt management, and token cost tracking to see which signals matter for your team. Deployment options, free-plan availability, and the paid starting point add practical considerations for fitting a tool to your stack. The ranked entries begin with Arize AX, Langfuse, and Opik, followed by W&B Weave and Helicone. Use the listed criteria to assess the coverage and operating choices each option offers.
25 LLM observability tools ranked on what their makers publish — plans and prices, free tiers, platforms and the facts on their own pages.
| # | Platform | Score | Why | From | Free plan | Paid from | LLM tracing | |
|---|---|---|---|---|---|---|---|---|
| 1 |  Arize AX | 8.9 | RecognisedAPIDocumented | $50/mo | Yes | 50 /mo | Yes | View |
| 2 | Langfuse | 8.9 | RecognisedAPIDocumented | $29/mo | Yes | 29 /mo | Yes | View |
| 3 | Opik | 8.8 | RecognisedAPIDocumented | $19/mo | Yes | 19 /mo | Yes | View |
| 4 | W&B Weave | 8.7 | RecognisedAPIDocumented | $60/mo | Yes | 60 /mo | Yes | View |
| 5 | Helicone | 8.3 | RecognisedAPIDocumented | $79/mo | Yes | 79 /mo | Yes | View |
| 6 |  OpenLIT | 8.1 | RecognisedAPIDocumented | Free | Yes | — | Yes | View |
| 7 | Evidently AI | 7.9 | RecognisedAPIDocumented | $80/mo | Yes | — | Yes | View |
| 8 | Galileo | 7.8 | RecognisedAPIDocumented | $100/mo | Yes | 100 /mo | — | View |
| 9 | Maxim AI | 7.7 | RecognisedAPIDocumented | $29/mo | Yes | — | — | View |
| 10 | Confident AI | 7.4 | RecognisedAPIDocumented | $200/mo | Yes | 200 /mo | — | View |
| 11 | Parea AI | 7.2 | RecognisedAPIDocumented | $150/mo | Yes | — | — | View |
| 12 |  Arize Phoenix | 7.0 | RecognisedAPIDocumented | — | Yes | — | Yes | View |
| 13 | LangSmith | 6.9 | RecognisedAPIDocumented | — | Yes | — | Yes | View |
| 14 | LangWatch | 6.8 | RecognisedAPIDocumented | — | Yes | — | Yes | View |
| 15 | Laminar | 6.7 | RecognisedAPIDocumented | $30/mo | Yes | 30 /mo | Yes | View |
| 16 | Fiddler AI | 6.6 | RecognisedAPIDocumented | — | Yes | — | Yes | View |
| 17 | HoneyHive | 6.4 | RecognisedAPIDocumented | — | Yes | — | Yes | View |
| 18 | AgentOps | 6.3 | RecognisedAPIDocumented | — | Yes | 40 /mo | Yes | View |
| 19 |  Respan (formerly Keywords AI) | 5.7 | RecognisedAPIDocumented | — | Yes | 199 /mo | Yes | View |
| 20 | Promptfoo | 5.6 | RecognisedAPIDocumented | Free | Yes | — | — | View |
| 21 | Giskard | 5.6 | RecognisedAPIDocumented | — | Yes | — | — | View |
| 22 |  Lunary | 5.4 | RecognisedAPIDocumented | — | No | — | Yes | View |
| 23 |  OpenLLMetry | 5.4 | RecognisedAPIDocumented | — | Yes | — | Yes | View |
| 24 | Ragas | 4.9 | RecognisedAPIDocumented | — | Yes | — | — | View |
| 25 |  TruLens | 4.3 | RecognisedAPIDocumented | — | — | — | — | View |
Is your platform on this list?
Numbered spots on this list can be sponsored. They are labelled, and the editorial order and scores never change for payment.
Questions about this list
Which LLM observability tool is ranked first on Inferse?
Arize AX is ranked #1 of 25 with a score of 8.9. Langfuse is second and Opik third.
How many of these have a free plan?
12 of the 25 on this page publish a free plan on their own pricing pages.
Which is the cheapest paid option?
On this page, Opik has the lowest first paid tier we found: $19/mo.
How is this list ranked?
Ranked on what each maker publishes, open and connectable first: a public API, open-source code, the depth of its documentation and a free tier to try it on. Model lists are sorted by the figure in their title, exactly as each provider publishes it. Paid placements never change a rank.