<div class="dropdown"><button type="button" class="btn btn-primary dropdown-toggle" data-toggle="dropdown">Primary </button><div class="dropdown-menu"><a class="dropdown-item" href="#">Action</a><a class="dropdown-item" href="#">Another action</a><a class="dropdown-item" href="#">Something else here</a></div></div>

<div class="btn-group"><button type="button" class="btn btn-primary">Primary</button><button type="button" class="btn btn-primary dropdown-toggle dropdown-toggle-split" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"><span class="sr-only">Toggle Dropdown</span></button><div class="dropdown-menu"><a class="dropdown-item" href="#">Action</a><a class="dropdown-item" href="#">Another action</a><a class="dropdown-item" href="#">Something else here</a><div class="dropdown-divider"></div><a class="dropdown-item" href="#">Separated link</a></div></div>

<!-- Large button groups(default and split) --><div class="btn-group"><button class="btn btn-secondary btn-lg dropdown-toggle" type="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Large button </button><div class="dropdown-menu">... </div></div><div class="btn-group"><button class="btn btn-secondary btn-lg" type="button">Large split button </button><button type="button" class="btn btn-lg btn-secondary dropdown-toggle dropdown-toggle-split" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"><span class="sr-only">Toggle Dropdown</span></button><div class="dropdown-menu">... </div></div><!-- Small button groups(default and split) --><div class="btn-group"><button class="btn btn-secondary btn-sm dropdown-toggle" type="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Small button </button><div class="dropdown-menu">... </div></div><div class="btn-group"><button class="btn btn-secondary btn-sm" type="button">Small split button </button><button type="button" class="btn btn-sm btn-secondary dropdown-toggle dropdown-toggle-split" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"><span class="sr-only">Toggle Dropdown</span></button><div class="dropdown-menu">... </div></div>

<!-- Default dropup button --><div class="btn-group dropup"><button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Dropup </button><div class="dropdown-menu"><!-- Dropdown menu links --></div></div><!-- Split dropup button --><div class="btn-group dropup"><button type="button" class="btn btn-secondary">Split dropup </button><button type="button" class="btn btn-secondary dropdown-toggle dropdown-toggle-split" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"><span class="sr-only">Toggle Dropdown</span></button><div class="dropdown-menu"><!-- Dropdown menu links --></div></div>