I use Firefox with the "Allow sites to choose their own fonts" option unchecked, so everything displays in my preferred font. I like it this way. The only problem is that some irritating websites (e.g., Github and Tumblr) decide to use custom fonts not to display text, but to create icons from the glyphs. What I would like is a way to set more than one font as "allowed" in Firefox: if a site tries to use one of the allowed fonts, okay, otherwise it uses my fonts.

Similar problems are described in a Mozilla support question, a Firefox bug report and another question on here. I can find no satisfactory solution.

As far as I can tell, CSS-based solutions, such as a custom user stylesheet, can't work, because I can't use CSS to select based on what font a given site is trying to display. That is, in theory it could be possible to write a "second stage" CSS rule that selects only elements which have their CSS font-family attribute set to a certain font, but in practice (as far as I know) CSS doesn't allow that. This also seems to mean that the Stylish extension is not a solution.

As a test, I also tried downloading Github's octicon font and installing it on my system, hoping that this would let Firefox do auto font substitution for those glyphs (the way it does if I view text in other alphabets). It doesn't work.

The following criteria are essential for to consider something a "solution":

  1. It must be a whitelist, not a blacklist --- that is, it must say "these fonts are allowed" not "these fonts are not allowed" --- and the fallback behavior for non-whitelisted fonts must be to use my specified fonts. I'm not interested in solutions that require me to manually "enable" my-fonts-only behavior for certain websites. The default behavior has to be to use my fonts.
  2. It must be font-specific, not just site-specific. I don't want to, e.g., allow Github to use its own fonts. I want to allow Github to use only its dumb octicons fonts where it uses them, while using my fonts for the rest of the site UI. I'm okay with a solution that lets me restrict by font and site, though. Basically, I'd be okay with a solution where I can say "let anyone use font X" or "let only site Y use font X", but not one that only lets me say "let site Y use whatever fonts it wants".
  3. It must not involve me writing any kind of custom stylesheet or script per site. This means "you can write a greasemonkey script to do that" is not a solution unless there is an existing greasemonkey script that does it once and for all. I'm okay with installing something and setting it up, and obviously I'll have to manage the whitelist myself, but it's not a solution if I have to tweak the tool for each site (e.g., by modifying it to "know" about that site's particular CSS).

Is there any solution for this? I'm curious whether I'm the only one who actually uses the "don't let sites use their own fonts" option, and, if not, how other people deal with this annoyance.

  • I use Firefox with the "Allow sites to choose their own fonts" option checked and have the same problem. I looked into this a little once and it seemed to be related to some security "feature" it has that doesn't allow sites to use fonts from other servers (or something similar to that) -- so your whole premise may be incorrect. Anyway, I never found a solution or about:config tweak to fix it.
    – martineau
    Nov 20, 2013 at 9:00
  • Such a feature would also be a great privacy feature if it allowed you to choose the list of fonts JS could discover (as per Why is there so much information in the font list? from the Panopticlick FAQ: panopticlick.eff.org/faq.php)
    – Ash
    Nov 20, 2013 at 9:14
  • @martineau: At least for me, that's not an issue. It does work if I turn on "Allow sites to choose fonts", I just don't want to do that globally.
    – BrenBarn
    Nov 20, 2013 at 17:43
  • FWIW, the cause of my similar problem with the option checked is described in this article titled Firefox doesn’t allow cross-domain fonts. It sounds like only the web-site operator can solve it.
    – martineau
    Nov 20, 2013 at 18:59
  • Again, my issue has nothing to do with cross-domain fonts. The fonts I want to use are local to my computer.
    – BrenBarn
    Feb 28, 2014 at 18:51

1 Answer 1


Per your instructions, this is not an answer. Just a work around. I don't have enough rep to make this a comment. I use an AutoHotkey (their site of course uses those damn glyphs!) script to flip that checkbox. It makes changing back and forth a single keyboard shortcut option (control + I):

#IfWinActive Firefox ahk_Group Firefox
^I:: ; fix fonts
    SendInput {AltDown}{AltUp}t
    sleep 100
    SendInput o
    WinWaitActive Options ahk_class MozillaDialogClass ahk_exe firefox.exe,,5
    If ErrorLevel
    SendInput !a
    WinWaitActive Fonts ahk_class MozillaDialogClass ahk_exe firefox.exe,,5
    If ErrorLevel
    SendInput !a{enter}
    WinWaitActive Options ahk_class MozillaDialogClass ahk_exe firefox.exe,,5
    If ErrorLevel
    SendInput +{tab}{enter}

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