Strict-Transport-Security — Good Declare that a website is only accessible over a secure connection (HTTPS). X-Frame-Options — Good Indicate whether a browser should be allowed to render a page in a <frame>, <iframe>, <embed> or <object>. X-Content-Type-Options — Good Indicate that the MIME types advertised in the Content-Type headers should be followed and not be changed. Content-Security-Policy upgrade-insecure-requests Good Control resources the user agent is allowed to load for a given page. Referrer-Policy — Good Control how much referrer information should be included with requests. Clear-Site-Data — Good Control the data stored by a client browser for their origins. X-Permitted-Cross-Domain-Policies — Good Control whether a web client such as Adobe Flash Player or Adobe Acrobat has permission to handle data across domains. Permissions-Policy — New Allow and deny the use of browser features in a document or iframe. Cross-Origin-Embedder-Policy — New Configure embedding cross-origin resources into the document. Cross-Origin-Opener-Policy — New Ensure a top-level document does not share a browsing context group with cross-origin documents. Cross-Origin-Resource-Policy — New Request that the browser blocks no-cors cross-origin/cross-site requests to the given resource. X-XSS-Protection — Deprecated Deprecated. Stops pages from loading when they detect reflected cross-site scripting (XSS) attacks. Feature-Policy — Deprecated Deprecated. Replaced by the Permissions-Policy header. Expect-CT — Deprecated Deprecated. Opt in to reporting and/or enforcement of Certificate Transparency requirements. Public-Key-Pins — Deprecated Deprecated. Allows HTTPS websites to resist impersonation by attackers using mis-issued or otherwise fraudulent certificates.