CSP checker

What is a CSP Checker?

The CSP Checker reports the Content-Security-Policy HTTP header a website sends, a browser-enforced allowlist that restricts which sources scripts, styles, images, and other resources are allowed to load from.

Why CSP Matters

• XSS mitigation — A well-configured CSP is one of the strongest defenses against cross-site scripting attacks, since it can block inline scripts and untrusted script sources outright.
• Defense in depth — Even if an attacker manages to inject malicious markup, a strict CSP can prevent it from ever executing.
• Easy to get wrong — An overly permissive policy (or none at all) provides little protection, while an overly strict one can break legitimate site functionality if not tested carefully.