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Content Security Policies (CSPs)

A Content Security Policy (CSP) is an added layer of security that helps detect and mitigate certain types of attacks, including:

• Content/code injection
• Cross-site scripting (XSS)
• Embedding malicious resources
• Malicious iframes (clickjacking)

To learn more about configuring a CSP in general, refer to the Mozilla documentation ↗.

Cloudflare's CDN is compatible with CSP.

Cloudflare does not:

• Modify CSP headers from the origin web server (except when using Zaraz, to ensure the Zaraz script is always running ↗).
• Require changes to acceptable sources for first or third-party content.
• Modify URLs (besides adding the /cdn-cgi/ endpoint and Cloudflare Fonts that rewrites Google Fonts urls).
• Interfere with locations specified in your CSP.

If you require the CSP headers to be changed or added, you can change them using some Cloudflare products:

• If your website is proxied through Cloudflare, you can use a response header transform rule to replace or add CSP headers.
• If your website is hosted using Cloudflare Pages, you can set a _headers file to modify or add CSP headers.

To use certain Cloudflare features, however, you may need to update the headers in your CSP: