Comparison
LangSmith vs Online Evaluation
LangSmith and Online Evaluation are both common AI/LLM terms but cover different ideas. Here is a quick side-by-side.
When you would reach for LangSmith
LangSmith comes up when the question is fundamentally about infrastructure.
A LangChain app with one line of setup: every chain run shows up in the LangSmith trace UI with input, output, intermediate steps, and per-step costs.
When you would reach for Online Evaluation
After offline eval is solid and you have meaningful production volume. Stretch your eval coverage from a fixed set to a live one.
Phoenix running a faithfulness eval on 5% of production RAG traces, dashboard charts the rolling 7-day mean.
Frequently asked
What is the difference between LangSmith and Online Evaluation?
LangSmith: LangSmith is LangChain's commercial LLM observability and evaluation platform. It captures traces (LangChain-native and OTel), runs evaluations, manages prompt versions, and supports dataset curation. Online Evaluation: Online evaluation runs scoring functions over live production traffic — usually a sample of recent traces — to monitor quality continuously instead of relying solely on a fixed offline dataset.
When should I use LangSmith vs Online Evaluation?
LangSmith is the right concept when you are focused on infrastructure. After offline eval is solid and you have meaningful production volume. Stretch your eval coverage from a fixed set to a live one.
Are LangSmith and Online Evaluation the same thing?
No. LangSmith is infrastructure; Online Evaluation is evaluation. They are related but address different parts of the AI stack.