Sometimes this doesn't work though. I use Firefox at work, but I'm required to use Google Drive, and any pdf from Drive will automatically download to my default download location without prompting me. This may not be Mozilla's fault, but it's shitty that any site can just choose to ignore my preferences.

I have a similar problem on Android with forcing pinch to zoom. Sites can and do use code to forcibly resist this accessibility setting. Like, a lot of sites.