Tab bar
The fixed row of icons at the bottom of a mobile app that switches between its main sections and stays put wherever you are.
See it
What it is
A tab bar is the fixed strip of icon-plus-label buttons pinned to the bottom of a mobile app, switching between its top-level destinations and staying visible wherever you go. Apple calls it the tab bar (Instagram, Spotify, the App Store); Material Design calls the same thing bottom navigation.
Reach for it when the app has 3 to 5 equally important sections people move between constantly. Native apps usually go further and give each tab its own navigation stack: leave a tab six screens deep, come back, and you land exactly where you left off, and a tap on the already-active tab scrolls to top and then pops to the root. Those are conventions worth copying, not rules the pattern enforces. A web app with one shared history and a bottom bar is perfectly normal, so pick the navigation model on purpose rather than inheriting it by accident.
Gotcha: a tab bar is for destinations, not actions. Cramming a 'compose' or plus button in the middle breaks the mental model, even though half the apps you use do it. Two more: this is not the same as tabs inside a page (those switch panels in one context), and on modern phones you must pad for the home indicator with the bottom safe-area inset or your labels sit under the swipe bar.
Ask AI for it
Build a mobile tab bar: a fixed bottom strip with 4 items, each a stacked icon over a 10px label, evenly distributed, on a background with a hairline top border and a subtle blur. The active item uses the accent color for icon, label, and a filled icon variant; inactive items use a muted grey with outline icons. Add padding-bottom: env(safe-area-inset-bottom) so it clears the home indicator, give each item a 44px minimum touch target, mark up as a nav with aria-current='page' on the active item, and make a tap on the active tab scroll its view to the top.