Modal windows

Summary

• Principle.
• Core HTML base.
• ARIA roles, states and properties.
• Keyboard interactions.
• Expected behavior.
• Notes.

Principle

A modal window appears inside the current window, and is displayed above the page that calls it.

Modal windows take control of the current page as long as they are displayed on the screen.

Core HTML base

The HTML base of a modal window differs, depending on whether or not it has a title displayed on the screen.

Modal window with a title displayed on the screen

<div role="dialog" aria-modal="true" aria-labelledby="modal-heading">
  <button>Close</button>
  <h1 id="modal-heading">[Modal heading]</h1>
  [Modal content]
</div>

Modal window without a title displayed on the screen

<div role="dialog" aria-modal="true" aria-label="[Modal heading]">
   <button>Close</button>
   [Modal content]
 </div>

ARIA roles, states and properties

• role="dialog" must be applied to the container in the modal window
• aria-modal="true" must be applied to the container in the modal window
• If the title of the modal window is displayed on the screen, it must be attached to the modal window via the attribute aria-labelledby :
  • The title of the modal window must have an id attribute with a unique value.
  • The container of the modal window must have an aria-labelledby attribute with the value of the id attribute of the modal window title.
• If the title of the modal window is not displayed on screen, aria-label must be applied and provided on the modal window container.

Keyboard interactions

Tab

When the modal window is displayed, this key moves the keyboard focus successively through the interactive elements in the modal window. If the focus is on the last interactive element in the modal window when the tab is pressed the keyboard focus moves to the first interactive element in the modal window.

Shift + Tab

This key combination has the same behavior as the Tab key, but in the reverse order. If the keyboard focus is on the first interactive element in the modal window when the key combination is pressed, the focus moves to the last interactive element in the modal window.

Esc

When the modal window is displayed, the modal window closes and the keyboard focus is placed on the interactive element that triggered the modal window.

Expected behavior

When the modal window is displayed (open)

• The keyboard focus is dynamically placed on the first interactive element contained in the modal window.
• The keyboard focus must be confined to the modal window and tabulating must not be possible on the rest of the page (below the modal window).
• The modal window can be closed with the Esc key.

When the modal window is hidden (closed)

• The keyboard focus must be repositioned on the element that opened the modal window opening.
• Ideally, the modal window is removed from the DOM. However, if the modal window remains present in the source code, display: none or visibility: hidden must be applied to its container.

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