It is likely not Firefox forcing this, but the website that thinks you are in the German (DE) region and thus redirects you. Most websites do this automatically. You can check if the website has a language selector that allows to show the pages in English. I get https://www.pokemon.com/us/ , so you can try this link instead. See also the preferred languages. *Settings -> General -> Language and Appearance -> Language<br>Choose your preferred language for displaying pages *https://support.mozilla.org/en-US/kb/choose-display-languages-multilingual-web-pages You can use websites like these to see how your location is reported via a reverse DNS look up of your IP: *https://www.iplocation.net/ *https://whatismyipaddress.com/

Oh OK. Indeed, when I put: https://www.pokemon.com/us/ it stays in the US and doesn't flip BTW, in Switzerland, especially around Zurich they use German, probably that's why it is "forcing" the de