Height of an HTML select box (dropdown)

Confirmed.

The part that drops down is set to either:

  1. The height needed to show all entries, or
  2. The height needed to show x entries (with scrollbars to see remaining), where x is
    • 20 in Firefox & Chrome
    • 30 in IE 6, 7, 8
    • 16 for Opera 10
    • 14 for Opera 11
    • 22 for Safari 4
    • 18 for Safari 5
    • 11 in IE 5.0, 5.5
  3. In IE/Edge, if there are no options, a stupidly high list of 11 blanks entries.

For (3) above you can see the results in this JSFiddle


NO. It's not possible to change height of a select dropdown because that property is browser specific.

However if you want that functionality, then there are many options. You can use bootstrap dropdown-menu and define it's max-height property. Something like this.

$('.dropdown-menu').on( 'click', 'a', function() {
    var text = $(this).html();
    var htmlText = text + ' <span class="caret"></span>';
    $(this).closest('.dropdown').find('.dropdown-toggle').html(htmlText);
});
.dropdown-menu {
    max-height: 146px;
    overflow: scroll;
    overflow-x: hidden;
    margin-top: 0px;
}

.caret {
	  float: right;
    margin-top: 5%;
}

#menu1 {
    width: 160px; 
    text-align: left;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
   
<div class="container" style="margin:10px">
  <div class="dropdown">
    <button class="btn btn-default dropdown-toggle" type="button" id="menu1" data-toggle="dropdown">Tutorials
    <span class="caret"></span></button>
    <ul class="dropdown-menu" role="menu" aria-labelledby="menu1">
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  </div>
</div>