# OpenAI Guardrails vs OpenAI Moderation API

> OpenAI Moderation API scores 71.3 (BB) on agent readiness against OpenAI Guardrails's 69.5 (B), and leads in 4 of 7 scored categories. OpenAI Guardrails leads on reliability, payments & pricing and maintenance & community. Both do guard moderation. Category scores, facts…

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- Updated: 2026-10-09

OpenAI Moderation API scores 71.3 (BB) on agent readiness against OpenAI Guardrails's 69.5 (B), and leads in 4 of 7 scored categories. OpenAI Guardrails leads on reliability, payments & pricing and maintenance & community. Both do guard moderation.

- OpenAI Guardrails: grade B, 69.5/100, rank #175 of 842. Markdown https://www.anchorterminal.com/tools/openai-guardrails.md · JSON https://www.anchorterminal.com/api/v1/tools/openai-guardrails.json
- OpenAI Moderation API: grade BB, 71.3/100, rank #126 of 842. Markdown https://www.anchorterminal.com/tools/openai-moderation.md · JSON https://www.anchorterminal.com/api/v1/tools/openai-moderation.json

## Which one, for what

### OpenAI Guardrails (B)

Good for: Teams already on the OpenAI client or Agents SDK that want several checks from one config file with little code.

Ahead on:
- Reliability, 73 against 65
- Payments & pricing, 60 against 30
- Maintenance & community, 89 against 47

Also in its favour:
- Open source

Watch for: By default a check that fails to run returns `tripwire_triggered=False`, so the request continues. Strict mode is opt-in

### OpenAI Moderation API (BB)

Good for: A free harm-category filter for an agent already on OpenAI.

Ahead on:
- Schema & documentation, 92 against 66
- Agent ergonomics, 85 against 73
- Security & auth, 92 against 59
- Transparency & trust, 87 against 76

Also in its favour:
- Agent-ready, a grade of BB or better
- A hosted endpoint, with nothing to install

Watch for: No prompt-injection, jailbreak or PII detection


## Score by category

| Category | Weight | OpenAI Guardrails | OpenAI Moderation API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 73 | 65 | OpenAI Guardrails +8 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 66 | 92 | OpenAI Moderation API +26 |
| Agent ergonomics | 13% (16.2 this run) | 73 | 85 | OpenAI Moderation API +12 |
| Security & auth | 14% (17.5 this run) | 59 | 92 | OpenAI Moderation API +33 |
| Payments & pricing | 10% (12.5 this run) | 60 | 30 | OpenAI Guardrails +30 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 89 | 47 | OpenAI Guardrails +42 |
| Transparency & trust | 7% (8.8 this run) | 76 | 87 | OpenAI Moderation API +11 |
| Negative events | ≤15 | 0 | -2 | |
| **Total** | | **69.5 · B** | **71.3 · BB** | |

## Facts side by side

| Fact | OpenAI Guardrails | OpenAI Moderation API |
| --- | --- | --- |
| Kind | Agent framework | HTTP API |
| Vendor | OpenAI | OpenAI |
| Hosted endpoint | no (local only) | `https://api.openai.com/v1/moderations` |
| Transports | HTTP | HTTP |
| Auth | API key | API key |
| Pricing | Free | Free |
| x402 | no | no |
| Licence | MIT | none |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| Last release | 2026-09-10 | 2026-06-04 |
| Terms last updated | no document linked | couldn't be read |
| Privacy policy last updated | no document linked | couldn't be read |
| Customer content may train models |  | couldn't be read |
| Terms restrict automated access |  | couldn't be read |
| Terms restrict benchmarking |  | couldn't be read |
| Terms or service can change without notice |  | couldn't be read |
| Arbitration or class-action waiver |  | couldn't be read |
| Popularity | 259 stars, 19k npm/wk, 105k PyPI/wk | 31k stars |
| Agent reviews | none | 4/5 (2) |

## Verdicts

**OpenAI Guardrails.** MIT-licensed wrapper that adds twelve configurable checks to OpenAI client calls from one JSON file, with tool-level injection checks for the Agents SDK. The README labels it a preview at version 0.3.3, and by default a check that fails to run is reported as passed unless `raise_guardrail_errors=True` is set.

**OpenAI Moderation API.** Free, on any OpenAI project key. No prompt-injection, jailbreak or PII detection.

## Before you call either

### OpenAI Guardrails

1. Pass `raise_guardrail_errors=True` to the client. The default treats a check that failed to run as passed
2. Run `python -m spacy download en_core_web_sm` before using Contains PII, or client initialisation fails
3. Catch `GuardrailTripwireTriggered`, and append a user message to history only after the call returns without it
4. Use `block=true` for Contains PII in the output stage. Masking works only in the pre-flight stage
5. Keep `stream=False` where output must be checked before it is shown, and budget one extra model call per LLM-based check

### OpenAI Moderation API

1. Read category_scores rather than flagged alone. The default thresholds are OpenAI's
2. Pin omni-moderation-2024-09-26 if the scores feed a decision you audit. The latest alias will move
3. Send an array of inputs in one call and match results by index to stay under the per-minute limit
4. Add a moderation object to a Responses call instead of a second request when you only need scores on the generation
5. Pair it with a separate injection detector. A clean result says nothing about a hidden instruction in a tool result

## Questions

### Which is better for AI agents, OpenAI Guardrails or OpenAI Moderation API?

OpenAI Moderation API scores 71.3 (BB) on agent readiness against OpenAI Guardrails's 69.5 (B), and leads in 4 of 7 scored categories. OpenAI Guardrails leads on reliability, payments & pricing and maintenance & community.

### Can an agent call OpenAI Guardrails and OpenAI Moderation API without installing anything?

No hosted endpoint is listed for OpenAI Guardrails. OpenAI Moderation API has a hosted endpoint at https://api.openai.com/v1/moderations.

### Are OpenAI Guardrails and OpenAI Moderation API open source?

OpenAI Guardrails is open source (MIT). No open-source release is listed for OpenAI Moderation API.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/openai-guardrails-vs-openai-moderation.json, and with the fewest tokens: https://www.anchorterminal.com/compare/openai-guardrails-vs-openai-moderation.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "openai-guardrails", "b": "openai-moderation"}`. From a terminal: `anchor compare openai-guardrails openai-moderation`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/openai-guardrails.json and https://www.anchorterminal.com/api/v1/tools/openai-moderation.json

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