However, as long as there is any CSS file with more than 2 KB of unused code, Google PSI will always display the “Reduce Unused CSS” recommendation.
In these cases, the "Reduce unused CSS" opportunity might not move to the "Passed audits" section. The "Potential Savings" value, though, should be improved significantly.
Additionally, some CSS code may be used for future development or to support older browsers that may not be able to use modern CSS features.
Our Reduce Unused CSS feature may significantly reduce the amount of unused CSS on your website, but it may not completely remove all unused CSS.
This is because some CSS may be used only in certain conditions or on certain pages and may not be easily identified by automated tools or browser developer tools.
Reducing the unused CSS can be a complex job, which is why automated applications or plugins can be quite harsh on a website and cause visual issues.
But the best and most reliable method to do that is to manually evaluate the code and decide which CSS code is needed and which is not.