Starting in Firefox 91, Private Browsing Windows will favor secure connections to the Web by default. Mozilla said for every Website you visit, Firefox will automatically establish a secure, encrypted connection over HTTPS whenever possible.
How HTTPS By Default Works
Firefox 91 introduces HTTPS by Default policy in Private Browsing Windows represents a major improvement in the way the browser handles insecure Web page addresses. Whenever you enter an insecure (HTTP) URL in Firefox’s address bar, or you click on an insecure link on a Web page, Firefox will now try to establish a secure, encrypted HTTPS connection to the website. In the cases where the Website does not support HTTPS, Firefox will automatically fall back & establish a connection using the legacy HTTP protocol instead.
If you enter an insecure URL in the Firefox address bar, or if you click an insecure link on a Web page, Firefox Private Browsing Windows checks if the destination Website supports HTTPS. If YES: Firefox upgrades the connection & establishes a secure, encrypted HTTPS connection. If NO: Firefox falls back to using an insecure HTTP connection.
Mozilla said it expects that HTTPS by Default will expand beyond Private Windows in the coming months.
