HTTP Strict Transport Security

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HTTP Strict Transport Security (HSTS) is an opt-in security enhancement that is specified by a web application through the use of a special response header. Once a supported browser receives this header that browser will prevent any communications from being sent over HTTP to the specified domain and will instead send all communications over HTTPS.


Example of the HTTP strict transport security header

 Strict-Transport-Security: max-age=60000

If all subdomains are HTTPS to then the following header is applicable:

 Strict-Transport-Security: max-age=60000; includeSubDomains

Browser Support

Lowest Version Supported
Internet Explorer
no support

Server Side

The server side needs to inject the HSTS header.

For HTTP sites on the same domain it is recommended that a HSTS header be returned along with a permanent redirect to the HTTPS site.

An Apache HTTPd example that will permanently redirect a URL to the identical URL with a HTTPS scheme, and add a HSTS header for the client, is as follows:

<VirtualHost *:80>
       ServerAlias *
       Header Always set Strict-Transport-Security "max-age=16070400; includeSubDomains"
       RewriteEngine On
       RewriteRule ^(.*)$ https://%{HTTP_HOST}$1 [redirect=301]


HSTS Spec entry

MDN Docs for HSTS

OWASP TLS Protection Cheat Sheet

Firefox STS Support

Google Chrome STS Support