Hover effects are feedback, not decoration
A hover state answers a question the user is already asking: is this thing clickable? That's why the most effective hover effects are subtle and instant — they confirm interactivity rather than performing. A card that lifts 4px on hover communicates "you can click me" more clearly than one that spins.
Keep durations short. Interface feedback belongs in the 150–300ms range; anything slower feels laggy because the user has already decided to click. Save longer, more elaborate motion for entrances, where there's no pending interaction to delay.
The critical caveat: hover doesn't exist on touch
Roughly half of web traffic has no hover at all. On touch devices, a hover state typically fires on tap — after the user has already committed — so any information you hide behind hover is effectively invisible to them.
The rule that follows: hover may enhance, never reveal. If a caption, a menu, or a "delete" button only appears on hover, mobile users can't reach it. Where you need hover-only styling, scope it with @media (hover: hover) so touch devices skip it entirely rather than getting a sticky stuck-on state.
Always pair hover with focus
Keyboard users never trigger hover. Every hover effect on an interactive element should have a matching :focus-visible style, or the entire interface becomes untraceable when tabbing through it. Writing a:hover, a:focus-visible { … } costs nothing and is a WCAG requirement, not a nicety.
Why these effects stay smooth
Each effect here transitions transform, opacity, box-shadow or background-position — properties the browser can handle without recalculating layout. Animating width, height, margin or top on hover forces layout on every frame and is the usual cause of janky hover states on lower-powered devices.