BrowserCaptureMediaStreamTrack: restrictTo() method

The restrictTo() method of the BrowserCaptureMediaStreamTrack interface restricts a self-capture stream to a specific DOM element (and its descendants).

Syntax

restrictTo(restrictionTarget)

Parameters

restrictionTarget

A RestrictionTarget instance representing the element the stream should be restricted to, or null/undefined, in which case any previously-set restriction is removed from the track.

Return value

A Promise that resolves to undefined.

The promise will reject if:

• The track kind is not "video", or its readyState is not "live".
• The restriction target element no longer exists.
• The track being restricted is not a track captured from the user's screen.
• restrictionTarget is not a RestrictionTarget instance, null, or undefined.
• restrictionTarget was created in a tab other than the one being captured.

Examples

Basic restriction example

// Options for getDisplayMedia()
const displayMediaOptions = {
  preferCurrentTab: true,
};

// Create restriction target from DOM element
const demoElem = document.querySelector("#demo");
const restrictionTarget = await RestrictionTarget.fromElement(demoElem);

// Capture video stream from user's webcam and isolate video track
const stream =
  await navigator.mediaDevices.getDisplayMedia(displayMediaOptions);
const [track] = stream.getVideoTracks();

// Restrict video track
await track.restrictTo(restrictionTarget);

// Broadcast restricted stream in <video> element
videoElem.srcObject = stream;

See Using the Element Capture and Region Capture APIs for in-context example code.

Stopping the restriction

You can stop the restriction by making a call to restrictTo() on the same track, passing an argument of null to it:

// Stop restricting
await track.restrictTo(null);

Specifications

• Element Capture

See also

• Screen Capture API
• Using the Element Capture and Region Capture APIs