The Grid Has Changed

Looking back at Bootstrap 3, the 4 grid tiers (‘xs’, ’sm’, ‘md’ and ‘lg’ breakpoints) worked looked like this..

Bootstrap 3 large tier

Bootstrap 3 medium tier

Bootstrap 3 small tier

Bootstrap 3 extra small tier

As you can see in Bootstrap 3, the smallest breakpoint has a wide range of devices less than 768px in width. As a result, there’s no simple way to create different grid layouts for typical smartphone screens (~375px). There is also no way to distinguish between portrait and landscape mode on mobile devices.

The Bootstrap 4 Grid

Introducing the new XL grid tier

Looking ahead to Bootstrap 4, the new grid tier provides better support for typical smaller device widths. Now there are 5 tiers (or breakpoints) to support typical portrait and landscape screen widths.

Bootstrap 4 introduces a new grid breakpoint with the col-xl-* classes. This extra tier extends the media query range all the way down to 544 px (or 34 em based on the new sizing). Eventhough the new XL tier would make one think it’s been added to support extra large screens, it’s actually the opposite.

All the 3.x tiers slide up in 4.x, to fit in the new 544 px to 768 px tier at the bottom. While the old 3.x col-xs-* supported screen widths under 768 px, the new 4.x col-xs-* tier supports screen width under 544 px. This new smaller xs tier means improved support portrait smartphones.

Desktop and laptops