It turned out to be pretty easy; I hacked one up in a few hours and got it published on AMO: https://addons.mozilla.org/en-US/firefox/addon/override-text-encodi

It turned out to be pretty easy; I hacked one up in a few hours and got it published on AMO: https://addons.mozilla.org/en-US/firefox/addon/override-text-encoding/ https://addons.mozilla.org/en-US/firefox/addon/override-text... It's open-sourced on GitHub in case you're curious. It just overrides the Content-Type header on pages where you've turned it on, setting the `charset` parameter to whatever you select.