Browser DevTools’ CSS panel is the fastest way to diagnose a layout problem — faster than editing a file and reloading, and it shows you exactly what’s being applied and what’s being overridden.
The Essentials
- Styles panel — shows every matching rule, with strikethrough on overridden ones (the fastest specificity debugger there is)
- Computed panel — shows the final resolved value for every property, after all rules are applied
- Box model diagram — visualizes margin/border/padding/content sizes at a glance
- Layout badges — click the “flex” or “grid” badge next to an element to overlay its actual grid lines or flex axis directly on the page
Live-Editing Without Touching Source
Toggle properties on and off, edit values directly, or force pseudo-states like :hover and :focus (via the “force state” button) to debug styles that only apply conditionally — all without ever touching your source files, then copy the working value back once you’ve found it.