Ensuring information and operation are clear and consistent.
The Understandable principle is the bridge between perception and action. It ensures that the sights and sounds provided by your interface lead to clear, logical outcomes when a user "touches" or interacts with them. When a site is understandable, users don't just see the path—they know where it leads.
Make text content readable and understandable. This begins with defining the document language so that screen readers use the correct pronunciation rules for the "Sound" of your content.
Primary Implementation: Always including the lang attribute on the <html> tag and providing definitions for unusual words or abbreviations.
Make Web pages appear and operate in predictable ways. Users should never be surprised by a change of context when they simply move their focus or interact with a standard element.
Primary Implementation: Keeping navigation menus in the same location across all pages and ensuring that "touching" or clicking an element doesn't unexpectedly launch a new window or submit a form.
Master Predictable UI PatternsHelp users avoid and correct mistakes. When a user interacts with a form, the interface should provide clear labels and helpful error messages if something goes wrong.
Primary Implementation: Providing descriptive labels for all form fields and using clear, text-based error messages that explain how to fix a problem.
Examine Error Prevention & GuidanceWe often say a design is "intuitive," but intuition is built on experience. For users with cognitive disabilities or those using assistive technology, "intuitive" simply means predictable. If your navigation moves or your icons change meaning from page to page, you've broken the user's trust and made your site inaccessible.