The :hover pseudo-class applies styles when a user hovers their cursor over an element. It's one of the most commonly used CSS pseudo-classes for creating interactive UI feedback — such as button color changes, link underlines, and card lift effects. On touch devices, :hover may behave differently or require a tap to trigger, which is why testing with a simulator is valuable.

The :active pseudo-class is triggered during the moment a user presses down on an element (between mousedown and mouseup). It's commonly used to create a "pressed" visual effect — like a button appearing depressed, a slight scale reduction, or a darker background. This state is brief and hard to inspect without a simulator that can lock it.

The :focus pseudo-class applies when an element receives keyboard focus (via Tab navigation or programmatic focus). It's essential for accessibility — providing visible indicators for keyboard users. Common focus styles include outline rings, border color changes, and box shadows. Browsers have default focus styles, but custom designs often override them for aesthetic reasons.

A hover state simulator lets you lock and inspect transient CSS states (:hover, :active, :focus) without needing to physically maintain a cursor position or keyboard focus. This is especially useful for: debugging complex transitions, testing on mobile devices (where hover behaves differently), taking screenshots of specific states, and fine-tuning animations frame-by-frame.

Mobile devices don't have a traditional hover cursor. Browsers on touch devices often trigger :hover on the first tap and :active / click events on the second tap. With this simulator, you can lock the hover or active state on any element and see exactly how it looks — no device switching required. Simply toggle the state buttons in the preview panel.

Yes! You can toggle Hover + Focus, Active + Focus, or even all three at once. This simulates real-world scenarios like a focused input being hovered, or a button being pressed while focused. The simulator adds CSS classes (.hover-sim, .active-sim, .focus-sim) alongside native pseudo-classes for full coverage.

:focus-visible applies focus styles only when the browser determines the user is navigating via keyboard (not mouse click). :focus-within matches an element if it or any descendant has focus — great for highlighting form groups. This simulator primarily targets :hover, :active, and :focus, but you can manually write CSS for :focus-visible and test it by using Tab to navigate.

• Use transition for smooth state changes (e.g., transition: all 0.2s ease)
• Ensure :focus styles have sufficient contrast for accessibility (WCAG 2.1 requires a visible focus indicator)
• Combine :hover and :focus for comprehensive interaction coverage
• Keep :active brief and snappy — users expect instant feedback
• Avoid :hover-only critical functionality — it excludes touch and keyboard users
• Test with this simulator to ensure all states look polished!