Basic dropdown
Wrap the dropdown’s toggle (your button or link) and the dropdown menu within .dropdown
Dropdown outline
Add class .btn-outline-{color}
to the button inside .dropdown
Split button dropdowns
Wrap two buttons in .btn-group
and add .dropdown-toggle-split
to the toggling button
Icon dropdowns
Replace button with icon buttons
Dropup variation
Add class .dropup
Dropdown sizes
Add class .btn-{size}
to dropdown buttons