Alternatives / LangSmith
Looking for an open source LangSmith alternative? We compared 8 open source LLM observability platforms by license, tracing, evaluation, OpenTelemetry support, and self-hosting. Most can be self-hosted for free, and several keep enterprise features under commercial licenses.
Written by Maxime DERAME
Last updated:
| Alternative | Best for | License |
|---|---|---|
| Langfuse | Closest tracing, evaluation, and prompt management (has ee folders) | MIT + ee folders |
| Arize Phoenix | Tracing and evaluation (source available) | Elastic License 2.0 (source available) |
| OpenLLMetry | OpenTelemetry instrumentation library | Apache-2.0 |
| Helicone | Proxy-based logging and monitoring | Apache-2.0 |
| Latitude | Monitoring and fixing AI agents | MIT |
| LangWatch | Agent testing and evaluation (enterprise modules) | Apache-2.0 + enterprise modules |
| OpenLIT | OpenTelemetry-native GenAI observability | Apache-2.0 |
| Spanlens | Simple drop-in proxy (very young) | MIT |
We looked for open-source tools that overlap with LangSmith's core: tracing LLM calls, evaluating outputs, managing prompts, and monitoring cost and latency. We verified each project's license, recent activity, stars, and self-hosting in its repository. LangSmith works with any framework but is closely tied to LangChain, so we note framework support and flag source-available and open-core licenses. See our methodology for the full criteria.
Arize Phoenix is licensed under the Elastic License 2.0, which allows free use and self-hosting but prohibits offering it as a managed service and circumventing license-key features. It is source available rather than OSI open source, so check the terms if you build a product around it.
Langfuse is MIT except for its ee folders, which are under a separate license. LangWatch is Apache-2.0, but its enterprise modules in platform/app/ee need a commercial license in production. Check which features you need before assuming they are free to self-host.
Langfuse is the closest: tracing, evaluations, prompt management, datasets, and analytics, with self-hosting or a cloud service, and it works with many frameworks beyond LangChain. Arize Phoenix and LangWatch cover tracing and evaluation, and Latitude focuses on monitoring and fixing agents.
OpenLLMetry is an Apache-2.0 instrumentation library built on OpenTelemetry that sends traces to any compatible backend, so it is not a full dashboard on its own. OpenLIT combines OpenTelemetry-native instrumentation with a platform, and Helicone and Spanlens work as proxies in front of LLM providers.
Helicone, OpenLLMetry, OpenLIT, and LangWatch (core) are Apache-2.0. Langfuse, Latitude, and Spanlens are MIT, with Langfuse excluding its ee folders. Arize Phoenix is the Elastic License 2.0.
All eight projects were updated within weeks of this update. Spanlens is very young with 13 stars, so check its maturity before relying on it.
LangSmith is a proprietary hosted service from LangChain, priced by traces and seats, with self-hosting limited to enterprise plans, and your prompts and outputs are sent to its cloud. Open-source alternatives let you self-host for free, keep sensitive prompts on your own infrastructure, use OpenTelemetry standards, and avoid trace-based pricing, at the cost of running the stack and managing storage.
| Alternative | Type | License | Self-hosted | Best for |
|---|---|---|---|---|
| Langfuse | Observability platform | MIT + ee folders | Yes | Tracing and prompts |
| Arize Phoenix | Observability platform | Elastic License 2.0 | Yes | Tracing and evaluation |
| OpenLLMetry | Instrumentation library | Apache-2.0 | Library | OpenTelemetry users |
| Helicone | Proxy and platform | Apache-2.0 | Yes | Logging and routing |
| Latitude | Agent observability | MIT | Yes | Agent monitoring |
| LangWatch | Testing and observability | Apache-2.0 + enterprise modules | Yes | Agent evaluation |
| OpenLIT | OpenTelemetry platform | Apache-2.0 | Yes | GenAI monitoring |
| Spanlens | Proxy and dashboard | MIT | Yes | Simple setup |
Want the closest self-hosted LangSmith replacement
Langfuse offers tracing, evaluations, prompt management, and datasets under MIT, apart from its ee folders.
Want tracing and evaluation with a strong notebook workflow
Phoenix offers tracing, evaluation, and automatic instrumentation, but its Elastic License 2.0 is source available.
Already standardize on OpenTelemetry
OpenLLMetry adds LLM instrumentation to any OpenTelemetry backend under Apache-2.0, but it is a library, not a dashboard.
Want OpenTelemetry-native observability with a UI
OpenLIT provides real-time monitoring and distributed tracing for GenAI apps, built on OpenTelemetry under Apache-2.0.
Want a proxy for logging, caching, and routing
Helicone logs and monitors LLM requests through a proxy, under Apache-2.0, with an enterprise Helm chart on request.
Want to monitor and test AI agents
LangWatch offers simulation-based testing and observability, but its enterprise modules need a commercial license.
Want to find and fix where agents fail
Latitude is an MIT-licensed observability platform that traces agent failures and helps verify fixes.