Features and Benefits of Bootstrap 4
Sass Instead of LESS
Until now Bootstrap has used LESS as its main CSS prepocessor, but for the new major release, the style rules will be refactored to Sass, which is much more popular among frontend developers, has a huge contributor base, generally easier to use and offers more possibilities. Thanks to the powerful Libsass Sass Complier written in C/C++ Bootstrap 4 will compile much faster than before.
New Grid Tier for Smaller Screens
Bootstrap has a sophisticated responsive grid system that allows developers to target devices with different viewports. Bootstrap 3 currently has 4 grid classes for columns, .col-xs-XX for mobile phones, .col-sm-XX for tablets, .col-md-XX for desktops, and .col-lg-XX for larger desktops. Bootstrap 4 will enhance the grid system with a fifth one that will facilitate developers to target smaller devices under 480px viewport width.
The new grid class has taken the name of the previous smallest one, and pushed the current names of the grid tiers upwards by one notch. In Bootstrap 4 the large desktops will use the .col-xl-XX class selector. It’s important to know that despite the new name they didn’t add a new class for extra large screens but for extra small ones.