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What Is a CSP Header Builder?

A CSP header builder creates Content Security Policy headers through an interactive interface. CSP is one of the most important web security headers — it tells browsers exactly which content sources are trusted, blocking all others. But writing CSP directives by hand is notoriously error-prone, with a strict syntax and dozens of directives to configure.

This tool walks you through each directive, explains what it controls, and generates a valid CSP header string. It helps you build a policy that protects against XSS and injection attacks without accidentally blocking the scripts, styles, and resources your site needs to function.

How to Use This Tool

  1. Set your default source — Choose the fallback policy for all resource types. Most sites start with 'self' to allow only same-origin content by default.
  2. Configure each directive — Add allowed sources for scripts, styles, images, fonts, frames, and API connections. The tool explains each directive and provides common examples like CDN domains and analytics services.
  3. Enable reporting — Set a report-uri endpoint to receive CSP violation reports. Start with Report-Only mode to test your policy without breaking anything.
  4. Copy the header — The tool outputs the complete Content-Security-Policy header value along with server-specific implementation snippets for Apache (generate rules with our .htaccess Generator), Nginx, and common frameworks.

Tips and Best Practices

Frequently Asked Questions

What is a Content Security Policy?+
A Content Security Policy (CSP) is an HTTP response header that tells browsers which sources of content are allowed to load on your page. It prevents cross-site scripting (XSS), data injection, and clickjacking attacks by restricting where scripts, styles, images, fonts, and other resources can come from.
Why do I need CSP?+
CSP is one of the most effective defenses against XSS attacks. Even if an attacker finds an injection point in your HTML, CSP prevents their malicious script from executing because it was not loaded from an approved source. Major security frameworks and auditors require CSP headers.
What are the main CSP directives?+
The most important directives are default-src (fallback for all resource types), script-src (JavaScript sources), style-src (CSS sources), img-src (image sources), font-src (font files), connect-src (API and WebSocket endpoints), and frame-ancestors (who can embed your page).
What does Report-Only mode do?+
Content-Security-Policy-Report-Only sends violation reports to a specified endpoint without actually blocking content. This lets you test a CSP policy in production and see what would break before enforcing it.
How do I deploy the CSP header?+
Add the Content-Security-Policy header in your server configuration — Apache (.htaccess), Nginx (server block), or your application framework response headers. You can also use a tag, though this does not support all directives.
Will CSP break my website?+
A strict CSP can break functionality if it blocks legitimate resources. Start with Report-Only mode, review the violation reports to identify all required sources, then switch to enforcement mode once you have whitelisted everything your site needs.

📖 Learn More

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