Remove Unused css

hello
is it possible to remove unused CSS. when i check my site in google page speed insight i got an error for mobile speed "remove unused CSS" but i did not get any error for desktop speed. my mobile score is 80% and desktop score is 99%. i want to optimize the speed for mobile score. can any one guide me to do that.

I don't know of any optimization tool that can do it for you. You need to manually update your CSS by checking what class you are using in your html.

I guess you didn't write your CSS yourself? You are using Boostrap or something similar?