HTTP - Strict Transport Security (HSTS) - mandatory HTTPS

Strict Transport Security (HSTS) is a header that tell the client that the website should always be contacted with HTTPS

When HSTS is on, if it's not possible to make a https connection (for instance if the certificate is not valid), the user will not be able to navigate the website and will get this message.

Example with Apache - HTTP Header (mod_header module)

Header set Strict-Transport-Security "max-age=63072000; includeSubDomains"

To submit domains for hard coded inclusion in Chrome's HTTP Strict Transport Security (HSTS) preload list:

• Add the preload tag to the value

Header set Strict-Transport-Security "max-age=63072000; includeSubDomains; preload"

• and submit the website here: https://hstspreload.org/

In chrome

chrome://net-internals/#hsts

• then delete

• Strict-Transport-Security