Senior Frontend Interview Question About Web Performance

very important question comes up uh every almost in every front end engineering interview I've been doing what is critical CSS critical CSS is the name we give to the CSS Styles needed to display the styles of the elements uh that appear above the fold so basically imagine you land on a page and you see certain elements without scrolling critical CSS it's all the CSS we need to make those element uh position and to style them to ract it you can use certain module bundle plugins like the weback plugin it will basically render the application for the specific width and then it would use browser mechanism

like the CSS coverage to extract the CSS typ once you extracted critical CSS you can use it to improve the performance of your application by deferring alls except the critical CSS