Firefox developers have continued to develop the mode "“, when enabled, all calls made without encryption are automatically redirected to secure page options (“http://” is replaced by “https://”). In the nightly builds that will form the basis of the release of Firefox 25 on August 80, in the interface for configuring browser settings (about:preferences) in the "Privacy and security" section block to control enabling work only via HTTPS. the ability to enable this mode for all windows or only for windows opened in private browsing mode. By default, redirect to HTTPS is disabled.
Recall that the new regime decides with the default opening of pages using "http://", without the ability to change this behavior. Despite a lot of work to promote HTTPS in browsers, when typing a domain in the address bar without specifying a protocol, "http://" is still used by default. The proposed setting changes this behavior and also enables automatic replacement with "https://" when explicitly entering an address with "http://". In addition to replacing when you type in the address bar, switching to HTTPS is also done at the level of subresources loaded on pages.
If accessing the primary pages (entering the domain in the address bar) via https:// ends with a timeout, the user is shown an error page with a button for making a request via http://. In case of failures when loading on "https://" subresources loaded during page processing, such failures are ignored, but warnings are displayed in the web console, which can be viewed through the web developer tools.
Source: opennet.ru