None.

A Promise which is resolved when playback has been started, or is rejected if for any reason playback cannot be started.

The promise's rejection handler is called with a DOMException object passed in as its sole input parameter (as opposed to a traditional exception being thrown). Possible errors include:

NotAllowedError DOMException

Provided if the user agent (browser) or operating system doesn't allow playback of media in the current context or situation. The browser may require the user to explicitly start media playback by clicking a "play" button, for example because of a Permissions Policy.

NotSupportedError DOMException

Provided if the media source (which may be specified as a MediaStream, MediaSource, Blob, or File, for example) doesn't represent a supported media format.

Other exceptions may be reported, depending on browser implementation details, media player implementation, and so forth.

Although the term "autoplay" is usually thought of as referring to pages that immediately begin playing media upon being loaded, web browsers' autoplay policies also apply to any script-initiated playback of media, including calls to play().

If the user agent is configured not to allow automatic or script-initiated playback of media, calling play() will cause the returned promise to be immediately rejected with a NotAllowedError. Websites should be prepared to handle this situation. For example, a site should not present a user interface that assumes playback has begun automatically, but should instead update their UI based on whether the returned promise is fulfilled or rejected. See the example below for more information.

For even more in-depth information about autoplay and autoplay blocking, see our article Autoplay guide for media and Web Audio APIs.

This example demonstrates how to confirm that playback has begun and how to gracefully handle blocked automatic playback.

When this example is executed, it begins by collecting references to the <video> element as well as the <button> used to toggle playback on and off. It then sets up an event handler for the click event on the toggle button and attempts to automatically begin playback by calling the async playVideo() function.

A helper function toggleButton() lets us define what should happen in the code when we pass it a boolean value representing the playing state (e.g., toggleButton(true)) If playback is successful, the button text and its aria-label changes to "Pause". If playback fails, the button and aria-label shows "Play". This ensures that the playButton matches the playback state by watching for the resolution or rejection of the Promise returned by play():

<div class="video-box">
  <video
    id="video"
    width="480"
    loop
    src="https://developer.mozilla.org/shared-assets/videos/flower.mp4"></video>
  <button type="button" id="play-button" aria-label="Play"></button>
</div>

let videoElem = document.getElementById("video");
let playButton = document.getElementById("play-button");

playButton.addEventListener("click", handlePlayButton, false);
playVideo();

function toggleButton(playing) {
  if (playing) {
    playButton.textContent = "Pause";
    playButton.setAttribute("aria-label", "Pause");
  } else {
    playButton.textContent = "Play";
    playButton.setAttribute("aria-label", "Play");
  }
}

async function playVideo() {
  try {
    await videoElem.play();
    toggleButton(true);
  } catch (err) {
    toggleButton(false);
  }
}

function handlePlayButton() {
  if (videoElem.paused) {
    playVideo();
  } else {
    videoElem.pause();
    toggleButton(false);
  }
}

.video-box {
  position: relative;
}

#video {
  border: 2px solid black;
}

#play-button {
  position: absolute;
  top: 10px;
  left: 10px;
  padding: 8px 12px;
  background-color: black;
  color: white;
  border: none;
  cursor: pointer;
}

• Web media technologies
• Learning: HTML video and audio
• Autoplay guide for media and Web Audio APIs
• Using the Web Audio API