Bootstrap v4 has replaced the following classes: hidden-sm-down, hidden-md-down, hidden-lg-down, hidden-xl-down, hidden-xs-up, hidden-sm-up, hidden-md-up, hidden-lg-up, hidden-xl-up, hidden-xs, hidden-sm, hidden-md, hidden-lg, hidden-xl, visible-xs, visible-sm, visible-md, visible-lg, visible-xl
Below is an example of what classes you now need to have in order to reproduce the same effect as the above removed classes.
There is also an extension of the classes, as to what kind of display you can have: none, inline, inline-block, block, table, table-cell, flex and inline-flex.
Examples below are using the block extension.
hidden-xs-down = d-none d-sm-block
hidden-sm-down = d-none d-md-block
hidden-md-down = d-none d-lg-block
hidden-lg-down = d-none d-xl-block
hidden-xl-down = d-none (same as hidden)
hidden-xs-up = d-none (same as hidden)
hidden-sm-up = d-sm-none
hidden-md-up = d-md-none
hidden-lg-up = d-lg-none
hidden-xl-up = d-xl-none
hidden-xs (only) = d-none d-sm-block (same as hidden-xs-down)
hidden-sm (only) = d-block d-sm-none d-md-block
hidden-md (only) = d-block d-md-none d-lg-block
hidden-lg (only) = d-block d-lg-none d-xl-block
hidden-xl (only) = d-block d-xl-none
visible-xs (only) = d-block d-sm-none
visible-sm (only) = d-none d-sm-block d-md-none
visible-md (only) = d-none d-md-block d-lg-none
visible-lg (only) = d-none d-lg-block d-xl-none
visible-xl (only) = d-none d-xl-block
Above example taken from StackOverflow