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HTTP Observatory vs Security Headers: catalog facts
HTTP Observatory	Security Headers
Free Free to use on the MDN website.	Free Free to scan sites in the browser.
Web	Web
Checks CSP, HSTS and other security headers Actionable recommendations tied to MDN documentation	Simple A+ to F grade that is easy to share Option to hide results and follow redirects
Focuses on headers and configuration, not full vulnerability scanning Only works for publicly reachable sites	Scans appear in a public recent list unless hidden Covers headers only, not TLS or application flaws
Web application	Web application
Closed source	Closed source
License not stated	License not stated
Not stated if an account is needed	Not stated if an account is needed
Needs internet	Needs internet
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.