Are you saying the browser is not showing English, or the webpage? What about other webpages? Any problems?

If the webpage, try finding the language settings.

Please see the screenshot I attached to the original post. I set it to English, yet everything keeps being in Dutch. (tried restarting, changing to another language and back, etc. to no avail)

Note: it used to work so it seems a recent update broke it.

Maybe (re)install the English Firefox version as you currently may have a Dutch Firefox version. You can find the full version of the current Firefox release (65.0.2) in all languages and all operating systems here:

• https://www.mozilla.org/en-US/firefox/all/
• https://www.mozilla.org/en-US/firefox/65.0.2/releasenotes/

The about box is in English, so I guess I already have the English version. And as mentuioned above: it used to work, only recently stopped and switched to Dutch by itself

Firefox can only show the user interface in a different language when you have this specific locale installed or if you have a language pack for this language installed. Language packs are shown on "Options/Preferences -> Languages".

See also the "Internationalization & Localization" section on the "Help -> Troubleshooting Information" (about:support) page.

I had Dutch and US English installed (cannot remove Dutch). I now also added UK English, and that worked.

I had a similar problem just today (Mac OSX 10.14.5, Firefox 68.0). I have US and Norwegian keyboard installed on my MAc. At home, using external keyboard, no issue Firefox changing languages. I only have English language configured on Firefox.

Today, I worked from a coffee shop. FIrefox would change keyboard on my Mac. I'd go from one entry field to another and suddenly the keyboard would change. I'd set it back to US, do the same thing and it would change to Norwegian again. No keystrokes just clicking into the next field.

I thought I'd delete the Norwegian keyboard. But in Mac SysPref for Keyboard, I could not click the minus to get rid of Norwegian. I went to Safari and the same website I using when it switched keyboard and it did not switch keyboard.

So, something a bit odd it seems to be happening with the keyboard settings and Firefox.

I did notice when I got back home, the minus was now available on the Mac Keyboard SysPref.

Firefox stores some settings as part of the Site Preferences, so if you keep having problems then try to clear the Site Preferences via "Clear Recent History".