Black squares usually indicate a fault in font type. But I cant say this for sure. Try san serif, otherwise you can check out the answers in this post:
Font awesome is not showing icon
Best answer there:
In my case i made the following mistake in my css code.
*{
font-family: 'Open Sans', sans-serif !important;
}
This will override all font family rules for the entire page. My solution was to move the code to body like so.
body{
font-family: 'Open Sans', sans-serif;
}
NB: Whenever you use the !important flag in css, any other css rule declared of the same type on the same element will get overriden.
Answer By: Daniel Barde
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It also can depend on how you import the library, is it via the CDN or via a folder?
Via a CDN: Check if the path / url is correct (Maybe an unauthorised link?).
Via folder / download:
Maybe use"/fonts/fontawesome-free-5.3.1-web/css/all.css"
instead of
"/fonts/fontawesome-free-5.3.1-web/css/fontawesome.css".