Free and open first
Best LLM Observability Tools in 2026
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 apps
- Research read 23 Sept 2026
- How the order is worked out
- 1
AgentOps
Free plan Open source APISelf-hostedWebAgentOps brings tracing, replay, audit trails, and cost monitoring together for agent applications, with broad framework and provider integrations.
- 2
Evidently AI
Free plan Open source APILinuxMac+3Evidently AI covers evaluation, tracing, synthetic data and ongoing monitoring across AI and ML workflows. Review plan limits and support levels against the scale and deployment option you need.
- 3
Giskard
Free plan Open source APILinuxSelf-hosted+1 - 4
Langfuse
Free plan Open source APILinuxSelf-hosted+1Langfuse brings tracing, prompt workflows, and evaluation features into one AI engineering platform, with both hosted and self-hosted options.
- 5
LangWatch
Free plan Open source APILinuxMac+2LangWatch brings agent simulation, evaluation, tracing, and deployment options together for teams working toward production.
- 6
OpenLIT
Free plan Open source APILinuxMac+3Choose OpenLIT if you want LLM tracing, evaluations, prompt tools, and cost tracking, with the option to self-host under an Apache 2.0 license.
- 7
Lunary
Free plan Open source APISelf-hostedWebLunary combines LLM observability with analytics, prompt management, and response evaluation.
- 8
Opik
Free plan Open source APILinuxMac+3Opik brings tracing, evaluation, testing, and production monitoring into one platform, with both cloud and self-hosted options.
- 9
Promptfoo
Free plan Open source APILinuxMac+3Promptfoo combines prompt evaluation with red-team testing and a broad provider and integration list.
- 10
W&B Weave
Free plan Open source APIiPhoneLinux+4W&B Weave brings tracing, evaluation, monitoring, and safety scoring together for production AI agents.
- 11
TruLens
Free plan Open source APISelf-hostedTruLens offers tracing, evaluation, and version comparison for AI applications, with customizable metrics and self-hosted storage options.
- 12
Arize AX
Free plan APISelf-hostedWebArize AX combines tracing, evaluations and experiments with tools for investigating agent failures.
- 13
Arize Phoenix
Free plan APISelf-hostedWebPhoenix brings tracing, evaluation, prompt inspection, and dataset experiments to AI application teams. It is free and open source, with deployment choices and usage management left to users.
- 14
Braintrust
Free plan APISelf-hostedWebBraintrust combines production trace inspection with dataset evaluations and prompt iteration.
- 15
Confident AI
Free plan APISelf-hostedWebConfident AI brings development evaluations, production tracing, alerting, and safety testing into one platform. The free plan has defined usage limits, while paid plans start at $200 per month.
- 16
Fiddler AI
Free plan APISelf-hostedWeb - 17
Galileo
Free plan APISelf-hostedWebGalileo combines evaluation, observability, and guardrails with several deployment options and developer interfaces. Check the trace allowance and SSO availability against your deployment needs.
- 18
Helicone
Free plan APISelf-hostedWebHelicone brings routing and observability tools together, with a free tier and self-hosting options. Its maintenance-mode status is worth weighing when considering it for a new deployment.
- 19
LangSmith
Free plan APILinuxMac+3LangSmith combines agent evaluation with prompt tools and observability, including cost and trajectory tracking.
- 20
HoneyHive
Free plan APISelf-hostedWebHoneyHive covers trace inspection, evaluations, live monitoring, and version experiments for AI agents. Teams should compare the free plan’s limits with their event volume and retention needs.
- 21
Laminar
Free plan APISelf-hostedWebChoose Laminar if you need OpenTelemetry-native tracing and debugging for AI agents, with evaluations and cloud or self-hosted deployment options.
- 22
Maxim AI
Free plan APISelf-hostedWebMaxim AI brings prompt work, agent evaluation, and production observability into one platform.
- 23
OpenLLMetry
Free plan APISelf-hostedWebOpenLLMetry combines tracing, token cost tracking, and integrations for LLM applications in a free, Apache-2.0-licensed project.
- 24
Parea AI
Free plan APISelf-hostedWebParea combines LLM evaluation, prompt workflows, observability, and human review. Its free tier has stated team, log, retention, and prompt limits; the Team plan is $150 a month.
- 25
Respan (formerly Keywords AI)
Free plan APISelf-hostedWebRespan combines model routing with tracing, evaluation, and monitoring in one product. Check the gateway's possible latency and plan terms against your requirements before choosing it.
#1Places #1, #2, #3, #4, #5 on this list can be bought by the makers of the software on it. See the price
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