Keyboard
All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes, except where the underlying function requires input that depends on the path of the user's movement and not just the endpoints.
In plain language
If someone cannot use a mouse, they must still be able to operate every feature of the page using only a keyboard. That means links, buttons, menus, forms and other controls must all be reachable and usable with keys like Tab, Enter, Space, and arrow keys.
Why it matters
Keyboard access is essential for people who rely on assistive technologies, have motor impairments, or use devices that do not have a pointing device. If a page only works with a mouse, many users can become blocked and unable to complete tasks.
In practice
Fails this criterion
A dropdown menu only opens when clicked with a mouse, and the options cannot be selected with the keyboard. A keyboard user cannot interact with the menu at all.
Meets this criterion
The same dropdown can be focused with Tab, opened with Enter or Space, and navigated with arrow keys. All interactive controls can be activated and used without touching a mouse.
Test it yourself
Try using only the keyboard to navigate the page: press Tab, Shift+Tab, Enter, Space, and arrow keys. If you cannot reach or activate an interactive element, or if focus gets stuck, the criterion is failing.