How to optimize third-party css libraries?

Question

css

Is there any tool that would analyze html files and, based on the results of the analysis, generate one (or several) from third-party css files with only those classes that are used on the page?

Answer 1

There is such a methodology - BEM and a library for it bem - components . Only the styles that you use are collected there. (or indicated in dependencies)
For other libraries - this is not the case.

Answer 2

it is unlikely that this will happen, because styles can be loaded with js, and even come from the server.