LangSmith vs Promptfoo
Detailed side-by-side comparison to help you choose the right tool
LangSmith
🔴DeveloperAI Observability
LangSmith is LangChain's commercial observability, evaluation and prompt management platform for LLM apps and agents in production.
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FreePromptfoo
🔴DeveloperAI Evaluation
Open-source CLI and library for testing, evaluating, and red-teaming LLM prompts, models, and RAG pipelines — runs locally on your machine or in CI.
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FreeFeature Comparison
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💡 Our Take
Choose Promptfoo when you need security-oriented tests for prompts, RAG pipelines, agents, jailbreaks, and adversarial behavior before release. Choose LangSmith if your main workflow is tracing, debugging, and observing LangChain or LangGraph applications in development and production.
LangSmith - Pros & Cons
Pros
- ✓Best-in-class integration if you already use LangChain or LangGraph.
- ✓Eval suites are practical enough to actually gate releases on, not just dashboards.
- ✓Self-hosted Enterprise tier covers SOC 2 and regulated environments.
Cons
- ✗Per-trace pricing on Plus surprises teams that scale production traffic quickly.
- ✗Non-LangChain stacks work but trade ergonomic polish for SDK overhead.
- ✗Some eval features require additional LLM spend on top of the platform fee.
Promptfoo - Pros & Cons
Pros
- ✓Covers 6 product areas listed on the website: Red Teaming, Guardrails, Model Security, MCP Proxy, Code Scanning, and Evaluations.
- ✓Community plan is described as Free Forever and includes local or self-hosted operation, all LLM evaluation features, vulnerability scanning, and red teaming up to 10k probes per month.
- ✓Useful beyond prompt testing because it includes real-time guardrail positioning, model security monitoring, MCP Proxy protection, and IDE/CI/CD code scanning for LLM vulnerabilities.
- ✓Strong fit for regulated workflows because the website names 4 industry solution areas: Financial Services, Insurance, Telecommunications, and Real Estate.
- ✓Supports development workflows where evaluations and red-team checks can run before merge or release instead of relying only on post-deployment monitoring.
- ✓The site displays a public 20.6k metric alongside its open-source and community positioning, indicating substantial visible adoption or repository activity.
Cons
- ✗Public paid pricing is quote-based: Enterprise and On-Premise are listed as Custom rather than fixed monthly or annual prices.
- ✗The product surface is broad, so teams that only need simple prompt regression tests may find the security, guardrails, MCP proxy, and model-security positioning more than they need.
- ✗Red-teaming and evaluation quality still depend on well-designed test cases, assertions, graders, and representative datasets.
- ✗The website emphasizes development-time and security testing more than production observability, so teams may still need a tracing or monitoring platform alongside Promptfoo.
- ✗Enterprise suitability is clear, but self-serve details such as exact paid seat limits, usage caps beyond Community red-team probes, hosted data retention, and final contract terms are not visible in the public pricing content.
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