Answer by samcarter_is_at_topanswers.xyz for How to make all the fontawesome5 icons in a document small?

You could patch the command like this:

\documentclass{article}\usepackage{fontawesome5}\AddToHook{cmd/faIcon/before}{\begingroup\small}\AddToHook{cmd/faIcon/after}{\endgroup}\begin{document}some text before \faIcon{youtube} some text after...some text before \small\faIcon{youtube}\normalsize\ some text after...\end{document}

If you don't want a small icon, but just a smaller icon, you could use the relsize package:

\documentclass{article}\usepackage{fontawesome5}\usepackage{relsize}\AddToHook{cmd/faIcon/before}{\begingroup\smaller}\AddToHook{cmd/faIcon/after}{\endgroup}\begin{document}some text before \faIcon{youtube} some text after...some text before \small\faIcon{youtube}\normalsize\ some text after...{\Huge\faIcon{youtube}test}\end{document}