Guardrails AI
guardrailsai.comlibraryself-hosted
Guardrails AI is a self-hosted library in the Guardrails & Safety layer of the AI stack. Validators that check model output against a defined schema.
By Lattice editorial · Facts verified · method
- licence
- Apache-2.0
- language
- Python
- cost
- free
- owned by
- Production & Governance
Verified 2026-09build refuses it from 2027-04
Use Guardrails AI when
Validators that check output against a schema you define.
Skip Guardrails AI when
You need free-form moderation rather than structural checks.
Stops the bad input before it, and the bad output after. — that is what this layer of the stack is answerable for. See the full Guardrails & Safety section for the rest of the options.
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[](https://lattice.kunjshah.in/guardrails-safety/guardrails-ai)Quick answers
- Is Guardrails AI open source?
- Yes. Guardrails AI is open source under the Apache-2.0 licence. It is free to use.
- What are the alternatives to Guardrails AI?
- The closest alternatives to Guardrails AI are NeMo Guardrails and Invariant Guardrails.
Compared in
- Gateway vs guardrails vs evals: what to build firstA gateway, a guardrail layer and an eval suite compete for the same first week of work. What each catches, what each misses, and the order to adopt them in.
- NeMo Guardrails vs Guardrails AI vs Presidio vs InvariantSafety layers compared on input rails, output validation, PII handling and whether they run inline or as a separate service — with a recommendation by compliance shape.
Reading on guardrails
Alternatives to Guardrails AI
Listed as an alternative to
- NeMo GuardrailsNeMo GuardrailsProgrammable rails that constrain conversational flow.Use when Constraining conversational flow with programmable rails.Skip when You need deep semantic moderation — it is not a classifier.Apache-2.0 · self-hosted · free
- Invariant GuardrailsInvariant GuardrailsGuardrails as code, enforced inline in the call path.Use when Guardrails as code, enforced inline in the call path.Skip when Self-hosting is a hard requirement.proprietary · managed · usage-based
Also in guardrails
- NeMo GuardrailsNeMo GuardrailsProgrammable rails that constrain conversational flow.Use when Constraining conversational flow with programmable rails.Skip when You need deep semantic moderation — it is not a classifier.Apache-2.0 · self-hosted · free
- Llama GuardLlama GuardSafety classifier for prompt and response moderation.Use when One classifier covering both prompt and response moderation.Skip when You need domain-specific policy enforcement.Llama-3.1-Community · self-hosted · free
- Microsoft PresidioMicrosoft PresidioPII detection and anonymization for text and images.Use when Detecting and anonymising PII in text and images.Skip when Your data is already pseudonymised at source.MIT · self-hosted · free
- Lakera GuardLakera GuardPrompt injection and jailbreak detection at the gateway.Use when Prompt-injection and jailbreak detection at the gateway.Skip when Requests cannot leave your network.proprietary · saas · usage-based
- garakgarakScanner that probes models for known vulnerability classes.Use when Probing your own system for known vulnerability classes.Skip when You have no remediation path for whatever it finds.Apache-2.0 · self-hosted · free
- PyRITPyRITMicrosoft's red-team tool for generating and scoring attack prompts.Use when Generating and scoring attack prompts systematically.Skip when You are not authorised to test the target.MIT · self-hosted · free
- Invariant GuardrailsInvariant GuardrailsGuardrails as code, enforced inline in the call path.Use when Guardrails as code, enforced inline in the call path.Skip when Self-hosting is a hard requirement.proprietary · managed · usage-based