Strict-Transport-Security
Tells browsers to use HTTPS only for this host.
Response header (sent by servers) security
How it works
Prevents downgrade and cookie-stealing attacks on later visits. Recommended max-age is at least one year.
Example
Strict-Transport-Security: max-age=31536000; includeSubDomains
See it live: send any request in Endpoint Client and open the Headers tab, where every response header is explained. Specification: RFC 6797.
Related headers
Content-Security-Policy
Restricts what a browser page may load and run.
Cross-Origin-Resource-Policy
Which origins may embed this resource.
Permissions-Policy
Which browser features a page may use.
Referrer-Policy
How much of the current URL browsers send as Referer.
X-Content-Type-Options
Stops browsers from guessing the content type.
X-Frame-Options
Whether the page may be shown in a frame.