Promptfoo vs LangSmith: Which is Better in 2026?
Choosing between Promptfoo and LangSmith comes down to understanding what each tool does best. This comparison breaks down the key differences so you can make an informed decision based on your specific needs, not marketing claims.
Short on time? Here's the quick answer
We've tested both tools. Here's who should pick what:
Promptfoo
Build secure AI applications with AI security testing integrated into your development workflow.
Best for you if:
- • You need security features specifically
- • Integrates AI security testing into CI/CD and development workflows.
- • Automates context-aware attack generation and provides real-time threat intelligence.
LangSmith
Debug, monitor, and optimize your LLM applications and AI agents with comprehensive observability.
Best for you if:
- • You need AI agents features specifically
- • Debug LLM applications with detailed agent tracing.
- • Monitor key business metrics with live dashboards and alerts.
| At a Glance |  LangSmith | |
|---|---|---|
Starts at | $50/monthCloud | Free tier + paid plansFree tier available |
Best For | Security | AI Agents |
Rating | - | - |
Choose Promptfoo or LangSmith?
Choose Promptfoo if
Build secure AI applications with AI security testing integrated into your development workflow.
- LLM eval framework
- Open source
- Good for testing prompts
- Your work is security-shaped, not AI agents-shaped
Choose LangSmith if
Debug, monitor, and optimize your LLM applications and AI agents with comprehensive observability.
- Provides deep visibility into non-deterministic LLM behavior
- Helps improve application performance and response quality
- Offers comprehensive monitoring and alerting capabilities
- Your work is AI agents-shaped, not security-shaped
| Feature | Promptfoo | LangSmith |
|---|---|---|
| Pricing Model | Freemium | Freemium |
| User Rating | ★4.8/5 49 reviews | No ratings yet |
| Categories | SecurityTesting & QA | AI AgentsDeveloper Tools |
In-Depth Analysis
Promptfoo
Build secure AI applications with AI security testing integrated into your development workflow.
Strengths
- +LLM eval framework
- +Open source
- +Good for testing prompts
- +Active development
- +Good documentation
Weaknesses
- -Learning curve
- -CLI focused
- -Newer tool
- -Limited features
- -Still maturing
Key features
LangSmith
Debug, monitor, and optimize your LLM applications and AI agents with comprehensive observability.
Strengths
- +Provides deep visibility into non-deterministic LLM behavior
- +Helps improve application performance and response quality
- +Offers comprehensive monitoring and alerting capabilities
- +Identifies systemic issues and user needs automatically
- +Flexible integration with various frameworks and OTel
Weaknesses
- -Specific pricing details require visiting a separate page
- -Self-hosting is only available on the enterprise plan
- -Requires some setup (e.g., environment variables) to get started
Key features
Pricing: Promptfoo vs LangSmith
| Plan | Promptfoo | LangSmith |
|---|---|---|
| Tier 1 | Free Free | N/A |
| Tier 2 | $50 month Cloud | N/A |
| Tier 3 | custom Enterprise | N/A |
Pricing verified from each vendor's public pricing page. Compare in detail on Promptfoo pricing and LangSmith pricing.
Who Should Use What?
On a budget?
Both are freemium. Compare plans on their websites.
Go with: Promptfoo
Want the highest-rated option?
Neither has user reviews yet.
Go with: Promptfoo
Value user reviews?
Neither has user reviews yet.
Go with: Promptfoo
3 Questions to Help You Decide
What's your budget?
Both are freemium. Pricing won't help you decide here.
What's your use case?
Promptfoo is a security tool. LangSmith is in AI agents. Pick the category that matches your needs.
How important are ratings?
Neither has user reviews yet.
Key Takeaways
Promptfoo
- Free tier available
- Our pick for this comparison
LangSmith
- Better fit for AI agents
The Bottom Line
Promptfoo is our pick.
Frequently Asked Questions
Is Promptfoo or LangSmith better?
Promptfoo is rated in our evaluation. Both are freemium.
What are Promptfoo and LangSmith used for?
Promptfoo: Build secure AI applications with AI security testing integrated into your development workflow.. LangSmith: Debug, monitor, and optimize your LLM applications and AI agents with comprehensive observability..
What does Promptfoo cost vs LangSmith?
Promptfoo is freemium (free tier + paid plans). LangSmith is freemium (free tier + paid plans). Visit their websites for detailed pricing.