Microinteraction is a tiny, single-purpose moment in an interface: the system reacts to one action so the person knows something happened. A toggle that slides. A like that pulses. A password field that turns a requirement green as you type — form validation you can see.
They are UI details that serve UX and usability. They are not features and not full user flows — though a good onboarding or empty state uses them to confirm the first taps. Designer Dan Saffer described them as moments that complete one small task — trigger, rules, feedback, loops. Done well, they build trust: the product feels finished. Done badly or missing, people tap twice, wonder if checkout worked, or assume the site is broken.
A real-life example of a microinteraction
Someone hits Pay on a phone. For three seconds nothing moves. They tap again and get charged twice — or they close the tab. A spinner on the button, then a checkmark, is the microinteraction that prevents that. Same idea as a coffee shop that stamps your loyalty card in front of you: you saw the action land.
Use them to confirm, not to decorate. If the animation hides a slow checkout or a vague error, it is theater. For more examples, see Microinteractions: The Invisible Details and Small Gestures, Big Experiences.