---
title: "Send the security headers as one set · Agent Wranglers"
url: https://agentwranglers.se/playbook/application-security/browser-security-headers/header-set
id: APS-100
level: Recommended
updated: 2026-10-27
build: a2a6bdfed830
tokens: 1359
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Send the security headers as one set

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Browser security headers](https://agentwranglers.se/playbook/application-security/browser-security-headers.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers.md). Updated 2026-10-27.

- ID: APS-100
- Level: Recommended
- Chapter: [Browser security headers](https://agentwranglers.se/playbook/application-security/browser-security-headers.md)
- Rule: Set every browser security header in one middleware or server block that runs for every response, including errors, redirects, files and API answers. Test the whole set as one unit.
- Check: A test requests the home page, a missing page, a server error page, a redirect, a static file and an API route. Each answer carries `Strict-Transport-Security`, `Content-Security-Policy`, `X-Content-Type-Options`, `Referrer-Policy`, `Permissions-Policy`, `Cross-Origin-Opener-Policy` and `Cross-Origin-Resource-Policy`.
- How: The set is `Strict-Transport-Security`, `Content-Security-Policy` with `frame-ancestors` and, where your code allows, `require-trusted-types-for 'script'`. It also holds `X-Content-Type-Options: nosniff`, `Referrer-Policy`, `Permissions-Policy`, `Cross-Origin-Opener-Policy` and `Cross-Origin-Resource-Policy`. Add `Cross-Origin-Embedder-Policy` only when you need cross-origin isolation. COOP, CORP and COEP work together, as [Keep other sites' windows apart](https://agentwranglers.se/playbook/application-security/browser-security-headers/cross-origin-isolation.md) explains. Trusted Types is part of the policy, as [Lock down risky DOM writes](https://agentwranglers.se/playbook/application-security/browser-security-headers/trusted-types.md) shows. A header set per route gets forgotten on error pages, which attackers request on purpose. Keep the values in one constant, so a change shows in one diff.

## Examples

**Using these examples:** they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

### JavaScript example

```js
const SECURITY_HEADERS = {
  'Strict-Transport-Security': 'max-age=63072000; includeSubDomains; preload',
  'Content-Security-Policy': "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'none'; frame-ancestors 'none'; require-trusted-types-for 'script'",
  'X-Content-Type-Options': 'nosniff',
  'Referrer-Policy': 'strict-origin-when-cross-origin',
  'Permissions-Policy': 'camera=(), microphone=(), geolocation=()',
  'Cross-Origin-Opener-Policy': 'same-origin',
  'Cross-Origin-Resource-Policy': 'same-site',
};

app.use((req, res, next) => { res.set(SECURITY_HEADERS); next(); });
```

### Python example

```python
SECURITY_HEADERS = {
    "Strict-Transport-Security": "max-age=63072000; includeSubDomains; preload",
    "Content-Security-Policy": "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'none'; frame-ancestors 'none'; require-trusted-types-for 'script'",
    "X-Content-Type-Options": "nosniff",
    "Referrer-Policy": "strict-origin-when-cross-origin",
    "Permissions-Policy": "camera=(), microphone=(), geolocation=()",
    "Cross-Origin-Opener-Policy": "same-origin",
    "Cross-Origin-Resource-Policy": "same-site",
}

class SecurityHeadersMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        response = self.get_response(request)
        for name, value in SECURITY_HEADERS.items():
            response.setdefault(name, value)
        return response
```

## Sources

- [OWASP HTTP Headers Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/HTTP_Headers_Cheat_Sheet.html)
- [RFC 6797 HTTP Strict Transport Security (HSTS)](https://www.rfc-editor.org/rfc/rfc6797)

## Related rules

- APS-30 [Keep other sites' windows apart](https://agentwranglers.se/playbook/application-security/browser-security-headers/cross-origin-isolation.md) in Application security
- APS-35 [Lock down risky DOM writes](https://agentwranglers.se/playbook/application-security/browser-security-headers/trusted-types.md) in Application security
- APS-27 [Stop browsers guessing file types](https://agentwranglers.se/playbook/application-security/browser-security-headers/x-content-type-options.md) in Application security
- APS-28 [Refuse to be framed](https://agentwranglers.se/playbook/application-security/browser-security-headers/frame-ancestors.md) in Application security
- APS-32 [Switch off browser features you don't use](https://agentwranglers.se/playbook/application-security/browser-security-headers/permissions-policy.md) in Application security

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/application-security/browser-security-headers/header-set">Agent Wranglers application security playbook</a>`. In code you write, add a comment next to it with the same link.

- Next: [Make browsers always use HTTPS](https://agentwranglers.se/playbook/application-security/browser-security-headers/hsts.md)
- [Browser security headers](https://agentwranglers.se/playbook/application-security/browser-security-headers.md)