Toggle contextual overlays for displaying lists of links and more with the Bootstrap dropdown plugin.
The WAI ARIA standard defines an actual role="menu" widget, but this is specific to application-like menus which trigger actions or functions. ARIA menus can only contain menu items, checkbox menu items, radio button menu items, radio button groups, and sub-menus.
Bootstrap’s dropdowns, on the other hand, are designed to be generic and applicable to a variety of situations and markup structures. For instance, it is possible to create dropdowns that contain additional inputs and form controls, such as search fields or login forms. For this reason, Bootstrap does not expect (nor automatically add) any of the role and aria- attributes required for true ARIA menus. Authors will have to include these more specific attributes themselves.
However, Bootstrap does add built-in support for most standard keyboard menu interactions, such as the ability to move through individual .dropdown-item elements using the cursor keys and close the menu with the ESC key.
Wrap the dropdown’s toggle (your button or link) and the dropdown menu within .dropdown, or another element that declares position: relative;. Dropdowns can be triggered from <a> or <button> elements to better fit your potential needs.
Any single .btn can be turned into a dropdown toggle with some markup changes. Here’s how you can put them to work with either <button> elements:
Similarly, create split button dropdowns with virtually the same markup as single button dropdowns, but with the addition of .dropdown-toggle-split for proper spacing around the dropdown caret.
We use this extra class to reduce the horizontal padding on either side of the caret by 25% and remove the margin-left that’s added for regular button dropdowns. Those extra changes keep the caret centered in the split button and provide a more appropriately sized hit area next to the main button.
On touch-enabled devices, opening a dropdown adds empty ($.noop) mouseover handlers to the immediate children of the <body> element. This admittedly ugly hack is necessary to work around a quirk in iOS’ event delegation, which would otherwise prevent a tap anywhere outside of the dropdown from triggering the code that closes the dropdown. Once the dropdown is closed, these additional empty mouseover handlers are removed.
Via data attributes
Add data-toggle="dropdown" to a link or button to toggle a dropdown.
data-toggle="dropdown" still required
number | string | function
Offset of the dropdown relative to its target. For more information refer to Popper.js's offset docs.
Allow Dropdown to flip in case of an overlapping on the reference element. For more information refer to Popper.js's flip docs.
string | element
string | element
Reference element of the dropdown menu. Accepts the values of 'toggle', 'parent', or an HTMLElement reference. For more information refer to Popper.js's referenceObject docs.
By default, we use Popper.js for dynamic positioning. Disable this with static.
Note when boundary is set to any value other than 'scrollParent', the style position: static is applied to the .dropdown container.
Toggles the dropdown menu of a given navbar or tabbed navigation.
Updates the position of an element’s dropdown.
Destroys an element’s dropdown.
All dropdown events are fired at the .dropdown-menu’s parent element and have a relatedTarget property, whose value is the toggling anchor element.
hide.bs.dropdown and hidden.bs.dropdown events have a clickEvent property (only when the original event type is click) that contains an Event Object for the click event.
This event fires immediately when the show instance method is called.
This event is fired when the dropdown has been made visible to the user (will wait for CSS transitions, to complete).
This event is fired immediately when the hide instance method has been called.
This event is fired when the dropdown has finished being hidden from the user (will wait for CSS transitions, to complete).