This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The reason read-only property of the VRDisplayEvent interface returns a human-readable reason why the event was fired.


var myReason = vrDisplayEventInstance.reason;


A string representing the reason why the event was fired. The available reasons are defined in the VRDisplayEventReason enum, and are as follows:

  • mounted — The VRDisplay has detected that the user has put it on (or it has been otherwise activated).
  • navigation — The page has been navigated to from a context that allows this page to begin presenting immediately, such as from another site that was already in VR presentation mode.
  • requested — The user agent has requested that VR presentation mode be started. This allows user agents to include a consistent UI to enter VR across diferent sites.
  • unmounted — The VRDisplay has detected that the user has taken it off (or it has been otherwise slept/put on standby).


window.addEventListener('vrdisplaypresentchange', function(e) {
  console.log('Display ' + e.display.displayId + ' presentation has changed. Reason given: ' + e.reason + '.');


Specification Status Comment
WebVR 1.1
The definition of 'reason' in that specification.
Editor's Draft Initial definition

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic Support (Yes)1 2 (Yes)553 No ? ?
FeatureAndroidChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic Support No (Yes)4 ? ? No ? ?

1. Only works on desktop in an experimental version of Chrome (other builds won't return any devices when Navigator.getVRDisplays() is invoked).

2. , this feature is behind the WebVR preference. To change preferences in Chrome, visit chrome://flags.

3. Currently only Windows support is enabled by default. Mac support is available in Firefox Nightly.

4. Currently supported only by Google Daydream.

See also

Document Tags and Contributors

 Contributors to this page: fscholz, chrisdavidmills
 Last updated by: fscholz,