css - Scrollable Menu with Bootstrap - Menu expanding its container when it should not

Question

I tried this method (their fiddle) to enable scrollable menu with Bootstrap, but with that approach, the scrollable menu expands its container -- fiddle -- the non-scrollable menu, correctly, does not do this.

How can I fix this? Suggestions on other approaches compatible with Bootstrap are appreciated too!

---

For reference, here is the HTML from the first method's fiddle:

<ul class="nav">
    <li class="dropdown">
        <a class="icon-key icon-white" data-toggle="dropdown" href="#" style=
        "font-weight: bold"></a>

        <div class="dropdown-menu" style="margin-left: 2em">
            <ul class="dropdown-menu">
                <!-- static non-scrollable menu header 1 -->
            </ul>
        </div>

        <div class="dropdown-menu" style="margin-left: 2em">
            <ul class="dropdown-menu">
                <li class="disabled">
                    <a href="#"><i class="icon-group"></i> <b>My Groups</b></a>
                </li>

                <li>
                    <div class="dropdown-menu scroll-menu scroll-menu-2x"
                    style="margin-left: 2em">
                        <ul class="dropdown-menu scroll-menu scroll-menu-2x">
                            <li>
                                <a href="#">User</a>
                            </li>

                            <li>
                                <a href="#">Administrators</a>
                            </li>

                            <li>
                                <a href="#">Some Other Group</a>
                            </li>
                        </ul>
                    </div>

                    <ul class="dropdown-menu scroll-menu scroll-menu-2x">
                        <!-- Additional menu items omitted for brevity -->
                    </ul>
                </li>
            </ul>
        </div>

        <div class="dropdown-menu" style="margin-left: 2em">
            <ul class="dropdown-menu">
                <!-- static non-scrollable menu header 2 -->
            </ul>
        </div>

        <div class="dropdown-menu" style="margin-left: 2em">
            <ul class="dropdown-menu">
                <li class="disabled">
                    <a href="#"><i class="icon-user"></i> <b>My Roles</b></a>
                </li>

                <li>
                    <div class="dropdown-menu scroll-menu scroll-menu-2x"
                    style="margin-left: 2em">
                        <ul class="dropdown-menu scroll-menu scroll-menu-2x">
                            <li>
                                <a href="#">Core Users</a>
                            </li>

                            <li>
                                <a href="#">Admin</a>
                            </li>

                            <li>
                                <a href="#">Some Other Role</a>
                            </li>
                        </ul>
                    </div>

                    <ul class="dropdown-menu scroll-menu scroll-menu-2x">
                        <!-- Additional menu items omitted for brevity -->
                    </ul>
                </li>
            </ul>
        </div>

        <div class="dropdown-menu" style="margin-left: 2em">
            <ul class="dropdown-menu">
                <!-- static non-scrollable menu footer -->
            </ul>
        </div>

        <ul class="dropdown-menu">
            <li class="disabled">
                <a href="#"><i class="icon-chevron-up pull-left"></i> <i class="icon-chevron-up pull-right"></i></a>
            </li>
        </ul>
    </li>
</ul>

And the CSS:

/* So we wont impact the original bootstrap menu or it's pseudo call-out
arrow the menu is wrapped in a sub dropdown-menu with a chained scroll-menu */
ul.scroll-menu {
    position:relative;
    display:inherit!important;
    overflow-x:auto;
    -webkit-overflow-scrolling:touch;
    -moz-overflow-scrolling:touch;
    -ms-overflow-scrolling:touch;
    -o-overflow-scrolling:touch;
    overflow-scrolling:touch;
    top:0!important;
    left:0!important;
    width:100%;
    height:auto;
    max-height:500px;
    margin:0;
    border-left:none;
    border-right:none;
    -webkit-border-radius:0!important;
    -moz-border-radius:0!important;
    -ms-border-radius:0!important;
    -o-border-radius:0!important;
    border-radius:0!important;
    -webkit-box-shadow:none;
    -moz-box-shadow:none;
    -ms-box-shadow:none;
    -o-box-shadow:none;
    box-shadow:none
}

Answer 1

Bootstrap 5 (update 2021)

The dropdown markup has changed for BS 5 as the data- attributes have changed to data-bs-. However, setting max-height still works to make the dropdown scrollable...

.dropdown-menu {
    max-height: 280px;
    overflow-y: auto;
}

https://codeply.com/p/shJzHGE84z

Bootstrap 4 (update 2018)

The dropdown markup has changed for BS 4 as the items have their own dropdown-item class. However, setting max-height still works to make the dropdown scrollable...

.dropdown-menu {
    max-height: 280px;
    overflow-y: auto;
}

Bootstrap scrollable dropdown

Alternative horizontal menu for Bootstrap 4 using flexbox

---

Bootstrap 3 (original answer)

I think you can simplify this by just adding the necessary CSS properties to your special scrollable menu class..

CSS:

.scrollable-menu {
    height: auto;
    max-height: 200px;
    overflow-x: hidden;
}

HTML

       <ul class="dropdown-menu scrollable-menu" role="menu">
          <li><a href="#">Action</a></li>
          <li><a href="#">Another action</a></li>
          <li><a href="#">Something else here</a></li>
          <li><a href="#">Action</a></li>
            ..
          <li><a href="#">Action</a></li>
          <li><a href="#">Another action</a></li>
       </ul>

Working example: https://codeply.com/p/ox7JC49vmT