S.no Bootstrap 3 Bootstrap 4
1. It has 4 grid system It has 5 grid system
2. The offset class of Bootstrap 3 is (col-md-offset-4). The offset class of Bootstrap 4 is (offset-md-4).
3. In Bootstrap 3, this (.img-responsive) class is used for responsive image. In Bootstrap 4, this (.img-fluid) class is used for responsive image.
4. In Bootstrap 3 (.input-lg) and (.input-sm) is used to increase or decrease the input size. In Bootstrap 4 (.form-control-lg) and (.form-control-sm) is used to increase or decrease the input size.
BY Best Interview Question ON 31 Mar 2019