SUMMARY Modern browsers support looking up browsed domain in a list of domains that their owners desired for them to be HTTPS-only, even on the very first attempt to access the domain over plain HTTP (for the 2nd attempt you can use the Strict-Transport-Security header sent by the server, ASSUMING that you were not MITM'd in the initial connection if it was http://). This capability started (to my knowledge) with the Chromium/Chrome browser but the list public and all modern/popular browsers (Chrome, Edge, Firefox, IE) use it. My empiric attempts to go to http:// URLs with HSTS-preloaded domains using the Falkon browser did not result in an internal upgrade of the request to HTTPS. Some of these sites are not even listening on port 80, so I just end up being stuck until I realized I forgot the https:// prefix. Which makes me wonder if STS headers in general are also not respected? Anyway, it would be nice if Falkon looked up entered domains against the preload list and prepend https:// instead of http:// to such domains (and of course bar you from accessing the site should an invalid TLS cert was received as a result) STEPS TO REPRODUCE 1. Browse with domain only (so: http:// is prepended to the domain) to an HSTS-preloaded websites OBSERVED RESULT The connection is not automatically upgraded to HTTPS (unless the website itself does a 301/302, but that's not the issue I am reporting; I am talking about the browser itself upgrading the request to https:// even if it didn't get 301/302, and in fact, without even ATTEMPTING to connect of http:// to begin with.) EXPECTED RESULT Connection is automatically upgraded to https:// SOFTWARE/OS VERSIONS Linux/KDE Plasma: Arch Linux KDE Plasma Version: 6.3.5 KDE Frameworks Version: 6.14.0 Qt Version: 6.9.1 ADDITIONAL INFORMATION none