UI Bug

UI bugs affect how an application looks rather than how it functions. They include text that overlaps other elements, buttons that appear off-screen, images that stretch incorrectly, inconsistent spacing, mismatched fonts, and layouts that break at certain screen sizes. While they may not prevent the application from working, they erode user trust and create an impression of low quality.

AI code generation tools can produce visually impressive interfaces, but UI bugs often emerge at the boundaries: between different screen sizes, between light and dark modes, between different content lengths, or between different browsers. The AI typically generates CSS that works for a standard viewport but may not account for all the variations real users will encounter.

UI bugs are particularly important for vibecoded applications because visual quality is often the primary selling point. If the interface looks broken on a user's device, it undermines confidence in the entire application. Cross-browser and responsive testing by human testers catches these visual issues across the range of devices your users actually have.