Micro-interaction
A micro-interaction is a short animation in response to an action: button hover, form checkmark, loading state. It makes an interface feel alive.
These details, often under a second long, confirm that an action was registered: a button that changes color, a field that turns green on validation. They reassure without distracting.
Used well, micro-interactions build confidence in a form or conversion flow. Overused, they slow the interface down and irritate the visitor.