What are the most common UI design mistakes that affect usability?

The most common UI design mistakes include inconsistent component styling across pages (different button colors, font sizes, or spacing), interactive elements that are not visually distinguishable from static content, and icon-only navigation without text labels that forces users to guess function.

Other frequent errors are touch target sizes below 44×44 pixels on mobile, insufficient color contrast ratios that fail WCAG 2.1 AA standards, and overloading pages with too many competing visual priorities that prevent the eye from settling on a primary action. These issues compound on mobile devices where screen space is limited and precision interaction is harder. Figma’s accessibility plugins and browser-based tools like Axe identify these violations before development begins.