Visibility & Opacity

Visibility regressions are among the most treacherous because they let the pipeline believe everything is fine: the element is in the DOM, the unit tests pass, but visually it has vanished, is hidden behind another component, or is clipped by a parent container. This is exactly the scenario of a promotional banner still present in the code but invisible because of an overflow: hidden added elsewhere, or a mobile "Buy" button covered by a chat widget whose z-index was set too high. On business interfaces, a validation error message pushed to opacity 0 by a cascade side effect can silently break a critical operation without the operator understanding why. Common causes include header refactors that introduce overflow, z-index stacks poorly coordinated between teams, A/B tests partially reverted that leave forgotten display: none rules behind, opacity tweaks introduced for one visual effect but propagated too widely, or stylesheet conflicts that load in a different order in production. Delta-QA addresses this blind spot by comparing screenshots as rendered in the browser, not the raw DOM tree. If an element stops being visible, gets partially clipped, loses opacity, or ends up covered by another component, the visual diff calls it out clearly. The tool also captures interactive states, so you can verify that a dropdown, a modal, or an overlay stays correctly visible after each deployment, without having to manually reproduce every user journey on every page.