The XRSystem method isSessionSupported() returns a promise which resolves to true if the specified WebXR session mode is supported by the user's WebXR device. Otherwise, the promise resolves with false.

If no devices are available or the browser doesn't have permission to use the XR device, the promise is rejected with an appropriate DOMException.

mode

A String specifying the WebXR session mode for which support is to be checked. Possible modes to check for:

• immersive-ar Experimental
• immersive-vr
• inline

A Promise that resolves to true if the specified session mode is supported; otherwise the promise resolves to false.

Rather than throwing true exceptions, isSessionSupported() rejects the returned promise, passing to the rejection handler a DOMException whose name is one of the following strings.

SecurityError

Use of this feature is blocked by an xr-spatial-tracking Permissions Policy.

In this example, we see isSessionSupported() used to detect whether or not the device supports VR mode by checking to see if an immersive-vr session is supported. If it is, we set up a button to read "Enter XR", to call a method onButtonClicked(), and enable the button.

If no session is already underway, we request the VR session and, if successful, set up the session in a method called onSessionStarted(), not shown. If a session is already underway when the button is clicked, we call the xrSession object's end() method to shut down the WebXR session.

if (navigator.xr) {
  navigator.xr.isSessionSupported("immersive-vr").then((isSupported) => {
    if (isSupported) {
      userButton.addEventListener("click", onButtonClicked);
      userButton.textContent = "Enter XR";
      userButton.disabled = false;
    }
  });
}

function onButtonClicked() {
  if (!xrSession) {
    navigator.xr.requestSession("immersive-vr").then((session) => {
      xrSession = session;
      // onSessionStarted() not shown for reasons of brevity and clarity.
      onSessionStarted(xrSession);
    });
  } else {
    // Button is a toggle button.
    xrSession.end();
  }
}