The read-only droppedVideoFrames property of the VideoPlaybackQuality interface returns the number of video frames which have been dropped rather than being displayed since the last time the media was loaded into the HTMLVideoElement.

An unsigned 64-bit value indicating the number of frames that have been dropped since the last time the media in the <video> element was loaded or reloaded. This information can be used to determine whether or not to downgrade the video stream to avoid dropping frames.

Frames are typically dropped either before or after decoding them, when it's determined that it will not be possible to draw them to the screen at the correct time.

This example calls getVideoPlaybackQuality() to obtain a VideoPlaybackQuality object, then determines what percentage of frames have been dropped. That value is then presented in an element for the user's reference.

const videoElem = document.getElementById("my_vid");
const percentElem = document.getElementById("percent");
const quality = videoElem.getVideoPlaybackQuality();

const dropPercent =
  (quality.droppedVideoFrames / quality.totalVideoFrames) * 100;
percentElem.innerText = Math.trunc(dropPercent).toString(10);

• The HTMLVideoElement.getVideoPlaybackQuality() method, which creates and returns VideoPlaybackQuality objects