ConsistentHTTPS od Marat Tanalin

Caution: the extension does not prevent opening a site via HTTP and does nothing if the site is opened via HTTP and not via HTTPS. It is not an equivalent of addons like HTTPS Everywhere.

Automatically replaces the http protocol with the https in links and forms that lead to pages of the same site (optionally including its subdomains).

The extension does not use any predefined URL databases and solely relies on the fact of opening the current page via the HTTPS protocol that guarantees the site supports HTTPS.