Firefox menus are shown in Spanish, while I explicitly downloaded English version and have English set as the only interface language. I happen to be on a Spanish version of Windows, but this should be irrelevant for Firefox. Note that the options are shown in English. I want the menus to be shown in English. In the attached image, note the mix of languages: Options in English, menus and tooltip in Spanish (actually some tooltips are in English, as in the second image). Note that Spanish is not listed as an interface language. (As a bonus, no matter how many times I press Remove on Canadian and UK English languages, they re-appear. Any way to get rid of them?) This problem happened recently; for a decade the menus were in proper English on the same Spanish version of Windows. I twice removed Firefox from the system (without deleting my data) and re-installed it from US English version, once from MSI, then from EXE, to no avail.