The MediaKeyMessageEvent.messageType read-only property indicates the type of message. It may be one of license-request, license-renewal, license-release, or individualization-request. 
 The MediaKeyMessageEvent.messageType read-only property indicates the type of message. It may be one of license-request, license-renewal, license-release, or individualization-request. 
One of the following:
license-requestlicense-renewallicense-releaseindividualization-request| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
messageType | 
42 | 13 | 38 | No | 29 | 12.1 | 42 | 42 | 38 | 29 | 12.2 | 4.0 | 
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    https://developer.mozilla.org/en-US/docs/Web/API/MediaKeyMessageEvent/messageType