Determine DRM system supported by browser

There are several websites offering such a check, like dash-player.com/browser-capabilities/ After having a closer look at how it is done, one can use something similar to:

// EME Check
var keySystems = {
  widevine: ['com.widevine.alpha'],
  playready: ['com.microsoft.playready', 'com.youtube.playready'],
  clearkey: ['webkit-org.w3.clearkey', 'org.w3.clearkey'],
  primetime: ['com.adobe.primetime', 'com.adobe.access'],
  fairplay: ['com.apple.fairplay']
};
var keySystemsCount = (function () {
  var count = 0;
  for (keysys in keySystems) {
    if (keySystems.hasOwnProperty(keysys)) {
      count += keySystems[keysys].length;
    }
  }
  return count;
})();

var testVideoElement = document.createElement('video');
var supportedSystems = [];
var unsupportedSystems = [];

var supportsEncryptedMediaExtension = function () {
  if (!testVideoElement.mediaKeys) {
    if (window.navigator.requestMediaKeySystemAccess) {
      if (typeof window.navigator.requestMediaKeySystemAccess === 'function') {
        console.log('found default EME');
        hasEME = true;
        var isKeySystemSupported = function (keySystem) {
          var config = [{initDataTypes: ['cenc']}];
          if (window.navigator.requestMediaKeySystemAccess) {
            window.navigator.requestMediaKeySystemAccess(keySystem, config).then(function (keySystemAccess) {
              supportedSystems.push(keySystem);
            }).catch(function () {
              unsupportedSystems.push(keySystem);
            });
          }
        };
        var keysys, dummy, i;
        for (keysys in keySystems) {
          if (keySystems.hasOwnProperty(keysys)) {
            for (dummy in keySystems[keysys]) {
              isKeySystemSupported(keySystems[keysys][dummy]);
            }
          }
        }
      }
    } else if (window.MSMediaKeys) {
      if (typeof window.MSMediaKeys === 'function') {
        console.log('found MS-EME');
        hasEME = true;
        var keysys, dummy, i;
        for (keysys in keySystems) {
          if (keySystems.hasOwnProperty(keysys)) {
            for (dummy in keySystems[keysys]) {
              if (MSMediaKeys.isTypeSupported(keySystems[keysys][dummy])) {
                supportedSystems.push(keySystems[keysys][dummy]);
              } else {
                unsupportedSystems.push(keySystems[keysys][dummy]);
              }
            }
          }
        }
      }
    } else if (testVideoElement.webkitGenerateKeyRequest) {
      if (typeof testVideoElement.webkitGenerateKeyRequest === 'function') {
        console.log('found WebKit EME');
        hasEME = true;
        var keysys, dummy, i;
        for (keysys in keySystems) {
          if (keySystems.hasOwnProperty(keysys)) {
            for (dummy in keySystems[keysys]) {
              if (testVideoElement.canPlayType('video/mp4', keySystems[keysys][dummy])) {
                supportedSystems.push(keySystems[keysys][dummy]);
              } else {
                unsupportedSystems.push(keySystems[keysys][dummy]);
              }
            }
          }
        }
      }
    } else {
      console.log('no supported EME implementation found');
      hasEME = false;
    }
  }
}

Simply run supportsEncryptedMediaExtension() and supportedSystems will be filled with the desired information.

Note that the config object should be extended to include the specific codec claims respective to your particular media. It isn't enough to just detect the key system as codec support sometimes depends on Guest OS dependencies.

var config = [{
     "initDataTypes": ["cenc"],
     "audioCapabilities": [{
          "contentType": "audio/mp4;codecs=\"mp4a.40.2\""
     }],
     "videoCapabilities": [{
          "contentType": "video/mp4;codecs=\"avc1.42E01E\""
     }]
}];

In addition to the information listed here, I want to mention that in Chrome, whether you are using https or not will affect the availability of navigator.requestMediaKeySystemAccess function.

In your development environment that probably is running on http, navigator.requestMediaKeySystemAccess will return undefined for Chrome whereas the same code will return a function in Firefox.

In your prod environment that has https, navigator.requestMediaKeySystemAccess will return a function both in Chrome and Firefox.

I had to give videoCapabilities flags to make this work.

function testEME() {
  // https://shaka-player-demo.appspot.com/support.html
  var keySysConfig = [{
    "initDataTypes": ["cenc"]
      //,"persistentState": "required"  // don't use or MacSafari "not supported"
      //,"persistentState": "required", "distinctiveIdentifier": "required"
      //,"audioCapabilities": [{
      //  "contentType": "audio/mp4;codecs=\"mp4a.40.2\""
      //}]
      ,"videoCapabilities": [{
    "contentType": "video/mp4;codecs=\"avc1.4D401E\"" // avc1.42E01E = ConstrainedLevel3, 4D401E=MainLevel3
    //,"robustness": "3000"
      }]
  }];           
        
  var keySystems = {
    playready: ['com.microsoft.playready.recommendation', 'com.microsoft.playready'
      , 'com.microsoft.playready.hardware', 'com.youtube.playready'],
    clearkey: ['webkit-org.w3.clearkey', 'org.w3.clearkey'],
    widevine: ['com.widevine.alpha'],
    primetime: ['com.adobe.primetime', 'com.adobe.access'],
    fairplay: ['com.apple.fairplay','com.apple.fps'
      , 'com.apple.fps.1_0', 'com.apple.fps.2_0', 'com.apple.fps.3_0']
  };
            
  for(keyArr in keySystems) {
    for(forItemIdx in keySystems[keyArr]) {
      let keySys = keySystems[keyArr][forItemIdx];
      try {
         navigator.requestMediaKeySystemAccess(keySys, keySysConfig).
         then(function(mediaKeySystemAccess) {
         //let mkConfig = mediaKeySystemAccess.getConfiguration();
         //let sFlags = "persistentState="+mkConfig.persistentState 
         //  + ", distinctiveIdentifier="+mkConfig.distinctiveIdentifier; 
        console.log(keySys + " supported"); //+" ("+sFlags+")");
      }).catch(function(ex) {
         console.log(keySys+" not supported (" + ex.name+" "+ex.message+")." );
      });
      } catch (ex) {
        console.log(keySys+" not supported (" + ex.name+" "+ex.message+").." );
      }
    }
  }
}