Guardrails AI

Guardrails AI is an open-source framework that adds a validation layer to LLM outputs.

Free + paidWebAPICLIOpen sourceLLM-based

Compare with book-to-skill Explore Guardrails AI alternatives

Overview

Guardrails AI is an open-source framework that adds a validation layer to LLM outputs. It uses RAIL to define structure and quality constraints, ensuring outputs are safe, formatted correctly, and free of hallucinations. It features automatic re-asking and corrective actions when validations fail.

Key features

RAIL specification for output definition
Real-time PII and toxicity filtering
Automatic re-asking mechanism
Guardrails Hub for shared validators
Structured data enforcement
Integration with LangChain and LlamaIndex

Pricing

Free + paidStarting price: Free (open source)

View pricing page

Verified on: 8/30/2026

Use cases

Preventing PII leakage in chatbots
Extracting structured JSON data
Hallucination detection and prevention
Ensuring corporate guideline compliance

Who it is for

AI EngineersLLM Application DevelopersData scientists

Integrations

LangChainLlamaIndexOpenAIVercel AI SDK

How we verified this

Company, pricing, and feature details come from the primary sources below and our latest verification pass. When sources disagree, the official source and the most recent check win.

Last verified 08/30/2026Verified sources: 1