Side-by-side pricing, features, and free plan comparison — everything you need to choose between LangSmith and OpenAI API.
Verified May 2026.
LangSmith: Observability, evaluation, and dataset management platform for LLM applications. OpenAI API: API access to GPT-4o, o3, and other OpenAI models via REST.
LangSmith starts from $39/mo. OpenAI API starts from Pay-as-you-go.
LangSmith: Yes, free plan available. OpenAI API: Yes, free plan available.
Affiliate disclosure: some links on this page earn us a commission if you sign up. Pricing verified manually.