Tool guide
Check Security Headers
Checking security headers helps you confirm whether the browser gets the protections you intended to send.
What A Good Check Covers
A useful check follows safe redirects, reads the final response, and shows both present and missing headers.
The most common headers to review are CSP, HSTS, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, and Permissions-Policy.
What To Fix First
For many sites, nosniff, a clear referrer policy, and framing protection are good early fixes because they are usually low risk.
Move carefully with HSTS and CSP. HSTS depends on healthy HTTPS, and CSP can break scripts, images, styles, fonts, frames, or API calls if it is too strict.
Why Production Can Differ
Your local app may send different headers than production because CDNs, proxies, hosting platforms, and middleware all get a chance to change the response.
Recheck after deployments, CDN changes, framework upgrades, and hosting migrations.
Common questions
How do I check security headers?
Enter the public URL in the Security Headers Checker. HeaderCheckr follows safe redirects and reads the final browser-facing response.
Which security header matters most?
It depends on the site. HSTS, framing protection, nosniff, referrer policy, and CSP are usually worth reviewing early.
Can a missing header hurt SEO?
Security headers are not a simple ranking switch, but they support trust, safe browsing, and production quality.
Can adding headers break my site?
Some can. CSP and Permissions-Policy should be tested carefully because they can block resources or browser features.