# Referrer Policy

> Referrer Policy is an Agent Skill for devops & security published in the thedaviddias/Front-End-Checklist repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

Use when reviewing HTTP response headers for privacy hardening on any website that handles authentication, session state, or sensitive URL parameters.

- Skill name: `referrer-policy`
- Category: [DevOps & Security](https://www.openparable.com/skill/devops-security/1)
- Source: https://github.com/thedaviddias/Front-End-Checklist/blob/HEAD/skills/referrer-policy/SKILL.md
- Repository: thedaviddias/Front-End-Checklist (73,218 GitHub stars when collected)

## SKILL.md

# Set a Referrer-Policy header

Without a Referrer-Policy, a password reset link like `https://example.com/reset?token=abc123` is included in the `Referer` header when the user clicks an external link on that page — leaking the token to third parties.

## Quick Reference

- Use `Referrer-Policy: strict-origin-when-cross-origin` — the recommended modern default
- `strict-origin-when-cross-origin` sends the full URL for same-origin requests, only the origin for cross-origin HTTPS, and nothing for HTTPS→HTTP
- Never use `unsafe-url` — it sends the full URL including path and query string to every external site
- Can be set via HTTP header, `<meta>` tag, or the `referrerpolicy` attribute on individual `<a>` and `<img>` elements
- Sensitive URLs (reset tokens, private IDs) in query strings can be exposed via the Referer header if policy is too permissive

## Check

Check whether the server sends a Referrer-Policy header and verify the value is appropriate. The recommended value is strict-origin-when-cross-origin. Check for any pages with sensitive URL parameters that could be leaked via the Referer header.

## Fix

Add Referrer-Policy: strict-origin-when-cross-origin to all HTTP responses. Configure it in your web server, CDN, or application framework. For pages with particularly sensitive URLs, consider no-referrer or same-origin.

## Explain

Explain what the Referer header contains, how a permissive Referrer-Policy can leak sensitive URL parameters to third parties, and what the difference is between the various Referrer-Policy values.

## Code Review

Review server config, headers, forms, and integration points related to Set a Referrer-Policy header. Flag exact responses, cookies, or browser behaviors that violate the rule, and verify them against the effective production-like response.

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For full implementation details, code examples, and framework-specific guidance,
see `references/rule.md`.

Rule page: https://frontendchecklist.io/en/rules/security/referrer-policy

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Source: https://www.openparable.com/skill/devops-security/referrer-policy (OpenParable). Cite the canonical URL above.