row-cols-1
row-cols-sm-1
row-cols-md-3
row-cols-lg-4

row-cols-1
row-cols-sm-2
row-cols-md-3
row-cols-lg-4

row-cols-1
column
row-cols-md-2
row-cols-xl-3
row-cols-xxl-4

Extra small is smaller than the div below this.

.row-cols-1
Column
Column
Column
Small starts here. This is 576 px.
.row-cols-sm-1
Column
Column
Column
.row-cols-sm-2
Column
Column
Column

Medium starts here. This is 768px.
.row-cols-md-2
Column
Column
Column
.row-cols-md-3
Column
Column
Column

Large starts here. This is 992 px.
.row-cols-lg-3
Column
Column
Column
.row-cols-lg-4
Column
Column
Column

Extra large starts here. This is 1200 px.
.row-cols-xl-4
Column
Column
Column

Extra extra large starts here. This is 1400 px.
Column
Column
Column
Column