Dropdown
CNo accessibility annotations are needed for dropdowns, but keep these considerations in mind if you are modifying Carbon or creating a custom component.
What Carbon provides
Carbon bakes keyboard operation into its components, improving the experience of blind users and others who operate via the keyboard. Carbon incorporates many other accessibility considerations, some of which are described below.
Keyboard interactions
A dropdown component and its variants multiselect and combobox are reached by
Tab, with navigation of the options by Up and Down arrow keys. However,
the keys for opening the component and selecting its options are different for
each variant.

Dropdowns are in the tab order and operable by Up and Down arrow keys, once opened.
The dropdown opens with Enter, Space or Down arrow, with focus moving to
the selected option. Options are selected with Space or Enter, which also
closes the dropdown. Pressing Esc or Tab closes a dropdown without changing
the selected option.

Need to update
The multiselect opens with Enter or Space, which are also used to toggle the
selection of any option. Once items are selected, a tag appears in the field,
showing a numerical representation of the number of items selected along with an
‘x’. Pressing Esc closes the multiselect. Pressing Delete while focus is in
the collapsed field will clear all selected options.

Need to update
The combobox has significantly different operation, since it is a combination of
a text input and a dropdown. Enter or Down arrow will open the list of
options, as will typing any character or string of characters (which will also
filter the list to only show items that match the typed string). Pressing Esc
will clear the input and collapse the list. Pressing Enter will select a
highlighted option and collapse the combobox. (If nothing is highlighted in the
list, pressing Enter will just toggle the combobox open and closed.) Space
cannot be used for selecting, as pressing it will submit a space character into
the filter string.

Need to update
Development considerations
Keep these considerations in mind if you are modifying Carbon or creating a custom component.
- The dropdown and multiselect variant use a
buttonwitharia-haspopup="listbox". - The combobox uses an input with
role="combobox",aria-autocomplete="list",aria-haspopup="listbox"andautocomplete="off". - The combobox uses
aria-controlsfor a div withrole="listbox". - All variants use
aria-expandedto track the state of the listbox. - See the ARIA authoring practices for combobox for more considerations.