Content Security Policy: Stop XSS Attacks With One HTTP Header

Content Security Policy (CSP) is the most powerful browser-side defense against XSS attacks. A single HTTP header tells the browser exactly which resources can load — blocking inline scripts, unauthorized domains, and malicious injections. Yet most sites don't use CSP because writing policies manually is error-prone.

What Is CSP Header Generator?

CSP is an HTTP response header that defines approved sources for scripts, styles, images, fonts, and other resources. Anything not explicitly allowed is blocked. Our CSP Header Generator builds policies interactively with common presets.

How to Use CSP Header Generator on DevToolHub

1. Open the CSP Header Generator tool on DevToolHub — no signup required.
2. Paste or enter your input data in the left panel.
3. See the result instantly in the output panel.
4. Copy the result or download it as a file.

Building a Practical CSP

Start restrictive and loosen as needed:

// Strict CSP (recommended starting point)
Content-Security-Policy:
  default-src 'self';
  script-src 'self' https://cdn.example.com;
  style-src 'self' 'unsafe-inline';
  img-src 'self' https: data:;
  font-src 'self' https://fonts.gstatic.com;
  connect-src 'self' https://api.example.com;
  frame-ancestors 'none';
  base-uri 'self';
  form-action 'self';

This policy allows scripts from your domain and one CDN, inline styles (for CSS-in-JS frameworks), images from HTTPS and data URIs, and API calls to your backend.

Pro Tips

• Start with report-only mode (Content-Security-Policy-Report-Only) to test without breaking your site
• Add 'unsafe-inline' for style-src if you use CSS-in-JS — but avoid it for script-src
• Use nonces or hashes instead of 'unsafe-inline' for script-src when possible
• frame-ancestors 'none' replaces X-Frame-Options for clickjacking prevention

When You Need This

• Preventing XSS attacks on web applications
• Blocking unauthorized third-party scripts and trackers
• Meeting compliance requirements (PCI DSS, SOC 2) for web security
• Protecting admin panels and sensitive internal tools from injection