This issue is going on for a few months already. At some point my Firefox lost the ability to display some Chinese characters. This is a big issue for me, because I use Chinese almost daily. They're not rarely used characters either. One examples is (you'll be able to see it, I am not): "问" (Now I see only two quotation marks but I know that there is a character in between them.) Here are the details of what's going on: When I enter Chinese characters on most websites (not all of them!), only some of them will be displayed, while others are invisible. Thus when I enter a whole phrase, it's difficult to check whether I made any mistakes. I know the characters are there, because I can move my cursor through the characters and it'll stay at the same place, internally counting that invisible character, when I move over one of those invisibles. Also when I write Chinese text messages, the other person never seems to be missing any characters from my messages. Also when I copy paste them into an editor, they're clearly there and visible. So what I've tried so far is only the following: I went to: about:preferences#content and then set a font, which I know can display the characters (WenQuanYi Micro Hei). Also I enabled the checkbox with the label "Allow pages to choose their own fonts, instead of my selections above". So either almost aaaaall of the websites I am using suddenly removed their own font choices (highly unlikely) and FF can't use the font set by me properly, or there is another issue at work here. I also tried with another profile, by starting FF using the command line: firefox -P A completely new profile, no addons installed or anything, but still some Chinese characters are missing. Information about my machine: OS: Xubuntu 14.04 Firefox Version: 44.0.2 (shouldn't really matter as this is going on for a long time now) (Any other information required?) Example for a website on which FF is displaying Chinese characters correctly: http://www.mdbg.net