Picture-in-Picture

1. Introduction

This section is non-normative.

Many users want to continue consuming media while they interact with other content, sites, or applications on their device. A common UI affordance for this type of activity is Picture-in-Picture (PiP), where the video is contained in a separate miniature window that is always on top of other windows. This window stays visible even when user agent is not visible. Picture-in-Picture is a common platform-level feature among desktop and mobile OSs.

This specification aims to allow websites to initiate and control this behavior by exposing the following sets of properties to the API:

• Notify the website when it enters and leaves Picture-in-Picture mode.

• Allow the website to trigger Picture-in-Picture mode via a user gesture on a video element.

• Allow the website to know the size of the Picture-in-Picture window and notify the website when it changes.

• Allow the website to exit Picture-in-Picture mode.

• Allow the website to check if Picture-in-Picture mode can be triggered.

The proposed Picture-in-Picture API is very similar to [Fullscreen] as they have similar properties. The API only applies to HTMLVideoElement at the moment but is meant to be extensible.

2. Examples

2.1. Add a custom Picture-in-Picture button

<video id="video" src="https://example.com/file.mp4"></video>

<button id="togglePipButton"></button>

<script>
  const video = document.getElementById('video');
  const togglePipButton = document.getElementById('togglePipButton');

  // Hide button if Picture-in-Picture is not supported or disabled.
  togglePipButton.hidden = !document.pictureInPictureEnabled ||
    video.disablePictureInPicture;

  togglePipButton.addEventListener('click', function() {
    // If there is no element in Picture-in-Picture yet, let’s request
    // Picture-in-Picture for the video, otherwise leave it.
    if (!document.pictureInPictureElement) {
      video.requestPictureInPicture()
      .catch(error => {
        // Video failed to enter Picture-in-Picture mode.
      });
    } else {
      document.exitPictureInPicture()
      .catch(error => {
        // Video failed to leave Picture-in-Picture mode.
      });
    }
  });
</script>

2.2. Monitor video Picture-in-Picture changes

<video id="video" src="https://example.com/file.mp4"></video>

<script>
  const video = document.getElementById('video');

  video.addEventListener('enterpictureinpicture', function(event) {
    // Video entered Picture-in-Picture mode.
    const pipWindow = event.pictureInPictureWindow;
    console.log('Picture-in-Picture window width: ' + pipWindow.width);
    console.log('Picture-in-Picture window height: ' + pipWindow.height);
  });

  video.addEventListener('leavepictureinpicture', function() {
    // Video left Picture-in-Picture mode.
  });
</script>

2.3. Update video size based on Picture-in-Picture window size changes

<video id="video" src="https://example.com/file.mp4"></video>

<button id="pipButton"></button>

<script>
  let pipWindow;
  const video = document.getElementById('video');
  const pipButton = document.getElementById('pipButton');

  pipButton.addEventListener('click', function() {
    video.requestPictureInPicture()
    .catch(error => {
      // Video failed to enter Picture-in-Picture mode.
    });
  });

  video.addEventListener('enterpictureinpicture', function(event) {
    // Video entered Picture-in-Picture mode.
    pipWindow = event.pictureInPictureWindow;
    updateVideoSize(pipWindow.width, pipWindow.height);
    pipWindow.addEventListener('resize', onPipWindowResize);
  });

  video.addEventListener('leavepictureinpicture', function() {
    // Video left Picture-in-Picture mode.
    pipWindow.removeEventListener('resize', onPipWindowResize);
  });

  function onPipWindowResize(event) {
    // Picture-in-Picture window has been resized.
    updateVideoSize(event.target.width, event.target.height);
  }

  function updateVideoSize(width, height) {
    // TODO: Update video size based on pip window width and height.
  }
</script>

3. Concepts

3.1. Request Picture-in-Picture

When the request Picture-in-Picture algorithm with video, userActivationRequired and playingRequired is invoked, the user agent MUST run the following steps:

1. If Picture-in-Picture support is false, throw a NotSupportedError and abort these steps.

2. If the document is not allowed to use the policy-controlled feature named "picture-in-picture", throw a SecurityError and abort these steps.

3. If video’s readyState attribute is HAVE_NOTHING, throw a InvalidStateError and abort these steps.

4. If video has no video track, throw a InvalidStateError and abort these steps.

5. OPTIONALLY, if the disablePictureInPicture attribute is present on video, throw an InvalidStateError and abort these steps.

6. If userActivationRequired is true and the algorithm is not triggered by user activation, throw a NotAllowedError and abort these steps.

7. If video is pictureInPictureElement, abort these steps.

8. If playingRequired is true and video is paused, abort these steps.

9. Set pictureInPictureElement to video.

10. Let Picture-in-Picture window be a new instance of PictureInPictureWindow associated with pictureInPictureElement.

11. Queue a task to fire an event with the name enterpictureinpicture at the video with its bubbles attribute initialized to true and its pictureInPictureWindow attribute initialized to Picture-in-Picture window.

It is RECOMMENDED that video frames are not rendered in the page and in the Picture-in-Picture window at the same time but if they are, they MUST be kept in sync.

When a video is played in Picture-in-Picture mode, the states SHOULD transition as if it was played inline. That means that the events SHOULD fire at the same time, calling methods SHOULD have the same behaviour, etc. However, the user agent MAY transition out of Picture-in-Picture when the video element enters a state that is considered not compatible with Picture-in-Picture.

Styles applied to video (such as opacity, visibility, transform, etc.) MUST NOT apply in the Picture-in-Picture window. Its aspect ratio is based on the video size.

It is also RECOMMENDED that the Picture-in-Picture window has a maximum and minimum size. For example, it could be restricted to be between a quarter and a half of one dimension of the screen.

3.2. Exit Picture-in-Picture

When the exit Picture-in-Picture algorithm is invoked, the user agent MUST run the following steps:

1. If pictureInPictureElement is null, throw a InvalidStateError and abort these steps.

2. Run the close window algorithm with the Picture-in-Picture window associated with pictureInPictureElement.

3. Unset pictureInPictureElement.

4. Queue a task to fire an event with the name leavepictureinpicture at the video with its bubbles attribute initialized to true.

It is NOT RECOMMENDED that the video playback state changes when the exit Picture-in-Picture algorithm is invoked. The website SHOULD be in control of the experience if it is website initiated. However, the user agent MAY expose Picture-in-Picture window controls that change video playback state (e.g., pause).

As one of the unloading document cleanup steps, run the exit Picture-in-Picture algorithm.

3.3. Disable Picture-in-Picture

Some pages may want to disable Picture-in-Picture mode for a video element; for example, they may want to prevent the user agent from suggesting a Picture-in-Picture context menu or to request Picture-in-Picture automatically in some cases. To support these use cases, a new disablePictureInPicture attribute is added to the list of content attributes for video elements.

The disablePictureInPicture IDL attribute MUST reflect the content attribute of the same name.

If the disablePictureInPicture attribute is present on the video element, the user agent SHOULD NOT play the video element in Picture-in-Picture or present any UI to do so.

When the disablePictureInPicture attribute is added to a video element, the user agent SHOULD run these steps:

1. Reject any pending promises returned by the requestPictureInPicture() method with InvalidStateError.

2. If video is pictureInPictureElement, run the exit Picture-in-Picture algorithm.

3.4. Auto Picture-in-Picture

Some pages may want to automatically enter and leave Picture-in-Picture for a video element; for example, video meeting web apps would benefit from some automatic Picture-in-Picture behavior when the user switches back and forth between the web app and other applications/tabs. To support these use cases, a new autoPictureInPicture attribute is added to the list of content attributes for video elements.

The autoPictureInPicture IDL attribute MUST reflect the content attribute of the same name.

The autoPictureInPictureElement is the video element, among all video elements with the autoPictureInPicture attribute currently set, whose autoPictureInPicture attribute was set most recently. Note that the autoPictureInPictureElement can have the disablePictureInPicture attribute set. In that case, as expected, it won’t be allowed to enter Picture-in-Picture mode in the request Picture-in-Picture algorithm.

When the visibility state of a top-level browsing context value switches from "visible" to "hidden", the user agent MAY run these steps:

1. If autoPictureInPictureElement is null, abort these steps.

2. If pictureInPictureElement is set, abort these steps.

3. Let video be autoPictureInPictureElement.

4. Let userActivationRequired be false.

5. Let playingRequired be true.

6. Run the request Picture-in-Picture algorithm with video, userActivationRequired, and playingRequired.

When the visibility state of a top-level browsing context value switches from "hidden" to "visible", the user agent MAY run these steps:

1. If autoPictureInPictureElement is null, abort these steps.

2. If pictureInPictureElement is autoPictureInPictureElement, run the exit Picture-in-Picture algorithm.

3.5. Interaction with Remote Playback

The [Remote-Playback] specification defines a local playback device and a local playback state. For the purpose of Picture-in-Picture, the playback is local and regardless of whether it is played in page or in Picture-in-Picture.

3.6. Interaction with Media Session

The API will have to be used with the [MediaSession] API for customizing the available controls on the Picture-in-Picture window.

3.7. Interaction with Page Visibility

When pictureInPictureElement is set, the Picture-in-Picture window MUST be visible, even when the Document is not in focus or hidden. The user agent SHOULD provide a way for users to manually close the Picture-in-Picture window.

The [Page-Visibility] specification defines a visibilityState attribute used to determine the visibility state of a top-level browsing context. The Picture-in-Picture window visibility MUST NOT be taken into account when determining the value returned by visibilityState.

3.8. One Picture-in-Picture window

Operating systems with a Picture-in-Picture API usually restrict Picture-in-Picture mode to only one window. Whether only one window is allowed in Picture-in-Picture mode will be left to the implementation and the platform. However, because of the one Picture-in-Picture window limitation, the specification assumes that a given Document can only have one Picture-in-Picture window.

What happens when there is a Picture-in-Picture request while a window is already in Picture-in-Picture will be left as an implementation detail: the current Picture-in-Picture window could be closed, the Picture-in-Picture request could be rejected or even two Picture-in-Picture windows could be created. Regardless, the User Agent will have to fire the appropriate events in order to notify the website of the Picture-in-Picture status changes.

4. API

4.1. Extensions to HTMLVideoElement

partial interface HTMLVideoElement {
  [NewObject] Promise<PictureInPictureWindow> requestPictureInPicture();

  attribute EventHandler onenterpictureinpicture;
  attribute EventHandler onleavepictureinpicture;

  [CEReactions] attribute boolean autoPictureInPicture;
  [CEReactions] attribute boolean disablePictureInPicture;
};

The requestPictureInPicture() method, when invoked, MUST return a new promise promise and run the following steps in parallel:

1. Let video be the video element on which the method was invoked.

2. Let userActivationRequired be true if pictureInPictureElement is null. It is false otherwise.

3. Let playingRequired be false.

4. Run the request Picture-in-Picture algorithm with video, userActivationRequired, and playingRequired.

5. If the previous step threw an exception, reject promise with that exception and abort these steps.

6. Return promise with the Picture-in-Picture window associated with pictureInPictureElement.

4.2. Extensions to Document

partial interface Document {
  readonly attribute boolean pictureInPictureEnabled;

  [NewObject] Promise<void> exitPictureInPicture();
};

The pictureInPictureEnabled attribute’s getter must return true if Picture-in-Picture support is true and the context object is allowed to use the feature indicated by attribute name picture-in-picture, and false otherwise.

Picture-in-Picture support is false if there’s a user preference that disables it or a platform limitation. It is true otherwise.

The exitPictureInPicture() method, when invoked, MUST return a new promise promise and run the following steps in parallel:

1. Run the exit Picture-in-Picture algorithm.

2. If the previous step threw an exception, reject promise with that exception and abort these steps.

3. Return promise.

4.3. Extension to DocumentOrShadowRoot

partial interface mixin DocumentOrShadowRoot {
  readonly attribute Element? pictureInPictureElement;
};

The pictureInPictureElement attribute’s getter must run these steps:

1. If the context object is not connected, return null and abort these steps.

2. Let candidate be the result of retargeting Picture-in-Picture element against the context object.

3. If candidate and the context object are in the same tree, return candidate and abort these steps.

4. Return null.

4.4. Interface PictureInPictureWindow

interface PictureInPictureWindow : EventTarget {
  readonly attribute long width;
  readonly attribute long height;

  attribute EventHandler onresize;
};

A PictureInPictureWindow instance represents a Picture-in-Picture window associated with an HTMLVideoElement. When instantiated, an instance of PictureInPictureWindow has its state set to opened.

When the close window algorithm with an instance of PictureInPictureWindow is invoked, its state is set to closed.

The width attribute MUST return the width in CSS pixels of the Picture-in-Picture window associated with pictureInPictureElement if the state is opened. Otherwise, it MUST return 0.

The height attribute MUST return the height in CSS pixels of the Picture-in-Picture window associated with pictureInPictureElement if the state is opened. Otherwise, it MUST return 0.

When the size of the Picture-in-Picture window associated with pictureInPictureElement changes, the user agent MUST queue a task to fire an event with the name resize at pictureInPictureElement.

4.5. Event types

enterpictureinpicture

Fired on a HTMLVideoElement when it enters Picture-in-Picture. It uses the EnterPictureInPictureEvent interface.

[
    Constructor(DOMString type, EnterPictureInPictureEventInit eventInitDict),
    Exposed=Window
]
interface EnterPictureInPictureEvent : Event {
    [SameObject] readonly attribute PictureInPictureWindow pictureInPictureWindow;
};

dictionary EnterPictureInPictureEventInit : EventInit {
    required PictureInPictureWindow pictureInPictureWindow;
};

leavepictureinpicture

Fired on a HTMLVideoElement when it leaves Picture-in-Picture mode.

resize

Fired on a PictureInPictureWindow when it changes size.

4.6. Task source

The task source for all the tasks queued in this specification is the media element event task source of the video element in question.

4.7. CSS pseudo-class

The :picture-in-picture pseudo-class MUST match any element element for which one of the following conditions is true:

• element is pictureInPictureElement.

• element is a shadow host and the result of retargeting its node document’s pictureInPictureElement against element is element.

5. Security considerations

This section is non-normative.

The API applies only to HTMLVideoElement in order to start on a minimal viable product that has limited security issues. Later versions of this specification may allow PIP-ing arbitrary HTML content.

5.1. Feature Policy

This specification defines a policy-controlled feature that controls whether the request Picture-in-Picture algorithm may return a SecurityError and whether pictureInPictureEnabled is true or false.

The feature name for this feature is "picture-in-picture".

The default allowlist for this feature is *.

6. Acknowledgments

Thanks to Jennifer Apacible, Zouhir Chahoud, Marcos Cáceres, Philip Jägenstedt, Jeremy Jones, Chris Needham, Jer Noble, Justin Uberti, Yoav Weiss, and Eckhart Wörner for their contributions to this document.