PictureInPictureWindow

const button = document.querySelector("button");
const video = document.querySelector("video");

function printPipWindowDimensions(evt) {
  const pipWindow = evt.target;
  console.log(
    `: ${pipWindow.width}x${pipWindow.height}px`,
  );
  // :
  // : 640x360px
}

button.onclick = () => {
  video.requestPictureInPicture().then((pictureInPictureWindow) => {
    pictureInPictureWindow.onresize = printPipWindowDimensions;
  });
};