[sugarpimpdorsey]

My installation of Firefox defaults to plain HTTP when I type a URL into the address bar. No amount of about:config fiddling seems to turn it off.

It is rubbish software, the developers routinely ignore fixing actual bugs in favor of new features, and I wish we had a better alternative that wasn't married to Google.

[seanhunter]

This works fine for me, so I don’t know what’s causing it to be different for you. The key in about:config is dom.security.https_only_mode and I have that set to “true”.

If you want to set this without using about:config you can go to Settings and search “https” you’ll see “https-only Mode” there and you can turn it on for all windows, private windows oonly or none. There is also an exception list should you want that.