How do I set a default font?
How do I change the default font and font size in FireFox?
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https://support.mozilla.org/en-US/kb/change-fonts-and-colors-websites-use If wanting to use a Extension https://addons.mozilla.org/en-US/firefox/addon/theme-font-size-changer/ also possible : https://www.howtogeek.com/334716/how-to-customize-firefoxs-user-interface-with-userchrome.css/
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