The "Operable" principle is a core part of web accessibility. It ensures that all users can navigate and interact with web content, regardless of how they access the site. For a website to be operable, you must make sure that users can move through menus, forms, and interactive components using more than just a mouse. Many users rely on keyboards, assistive devices, or alternative input methods. If your web interface only works with a mouse, it is not accessible to everyone.

A key aspect of operability is keyboard navigation. This means that every interactive element on your site—such as links, buttons, and form fields—should be reachable and usable with the keyboard alone. Typically, users navigate using the Tab key to move forward through focusable elements, and Shift + Tab to move backward. The Enter or Space keys are used to activate buttons or links.

Focus indicators are another vital part of operability. They provide a visible outline or highlight around the currently focused element, helping users who navigate with a keyboard to know exactly where they are on the page. Without clear focus indicators, users can easily become lost, unable to tell which element will respond to their next action.

To illustrate these concepts, consider a navigation menu. If the menu is only accessible by mouse, keyboard users cannot reach its links. By ensuring the menu is built with proper HTML and visible focus styles, you make it operable for everyone.