In Magento 2 CSS files can be merged into one single file that helps to optimize the site which increases page loading performance. Same goes for javascript files. You can also minify the merged CSS file and JavaScript file Magento system in the same place. Here is how you can merge CSS or JS files.
Merging CSS files in Magento 2:
Go to Admin panel -> Stores -> Settings -> Configuration -> Advanced -> Developer -> CSS Settings -> Merge CSS Files -> Choose Yes from the dropdown -> Save Config.
Merging CSS files in Magento 2:
Go to Admin panel -> Stores -> Settings -> Configuration -> Advanced -> Developer -> JavaScript Settings -> Merge JavaScript Files -> Choose Yes from the dropdown -> Save Config.
