[v56+] Type '''about:preferences#general'''<enter> in the address bar. Under '''fonts and colors, ''' press the '''Advanced''' button. Scroll to the bottom, turn on '''Allow Web Sites To Choose Their Own. ''' Make sure you haven't enabled a High Contrast theme in the OS settings&#46; *We have seen reports that this can be caused by a problem with fonts like Roboto or Helvetica that you have installed locally and that might be corrupted or are missing some variants. Also, make sure you allow pages to choose their own fonts and that you do not block remote (downloadable) fonts. *[https://support.mozilla.org/questions/1325619] Weird font on some website's *If you use uBlock Origin make sure not to "block remote fonts".