React useWindowSize hook

React, Hooks, State, Effect · Oct 18, 2021

Tracks the dimensions of the browser window.

  • Use the useState() hook to initialize a state variable that will hold the window's dimensions. Initialize with both values set to undefined to avoid mismatch between server and client renders.
  • Create a function that uses Window.innerWidth and Window.innerHeight to update the state variable.
  • Use the useEffect() hook to set an appropriate listener for the 'resize' event on mount and clean it up when unmounting.
const useWindowSize = () => {
  const [windowSize, setWindowSize] = React.useState({
    width: undefined,
    height: undefined,

  React.useEffect(() => {
    const handleResize = () =>
      setWindowSize({ width: window.innerWidth, height: window.innerHeight });

    window.addEventListener('resize', handleResize);


    return () => {
      window.removeEventListener('resize', handleResize);
  }, []);

  return windowSize;
const MyApp = () => {
  const { width, height } = useWindowSize();

  return (
      Window size: ({width} x {height})

ReactDOM.render(<MyApp />, document.getElementById('root'));

Written by Angelos Chalaris

I'm Angelos Chalaris, a JavaScript software engineer, based in Athens, Greece. The best snippets from my coding adventures are published here to help others learn to code.

If you want to keep in touch, follow me on GitHub or Twitter.

More like this