npm i breakpoint-hooks
pnpm add breakpoint-hooks
yarn add breakpoint-hooks

import { useIsMobile } from "breakpoint-hooks";

// "use client" Next/React 19+ users only <----
export default function myFunctionalComponent() {
  const isMobile = useIsMobile();

  return (
    <>
      <h1>Greatest website</h1>
      //Some mobile only stuff
      {isMobile && (
        <p>
          Only mobile users can read this cool paragraph
        </p>
        )}
    </h1>
  )
}

Note that in next.js 14+ OR React 19, you will need to use this in a client component so use the use client directive at the top of your component

useIsMobile
useIsTablet