When viewing source code on GitHub, their CSS specifies the following fonts:

font-family: SFMono-Regular,Consolas,Liberation Mono,Menlo,Courier,monospace;

Even though I have SFMono-Regular installed on my Mac (in ~/Library/Fonts/SFMono-Regular.otf), Firefox uses Menlo to render the element. Both Safari and Chrome correctly use SFMono.

How can I get Firefox to detect and use the fonts installed in ~/Library/Fonts?


From Mozilla Support

This can happen when Firefox has a problem to access locally installed fonts because of sandbox security issues.


You can set this pref to 2 or 1 on the about:config page to lower the sandbox security setting.

security.sandbox.content.level = 1
close and restart Firefox to make the change effective. 

If '1' still doesn't have effect then try '0' to disable the sandbox.

If this didn't work then undo/reverse the change and reset the pref via the right-click context menu to the default value.

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.


If you also have this problem on the about:config page then try to boot the computer in Safe Mode.

  • This didn't work. Even after disabling the sandbox entirely, Firefox still uses Menlo – 130e13a Jan 25 at 9:28

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