Detecting Custom Protocol Handler in Windows 8+ with Chrome

Hey I think you were on the right track. It is definitly not that easy but chrome so far was not my problem, more like Edge + IE but my solution is assuming they don't support the protocol if anything fails or they don't respond correctly which they do sometimes.

The blur/focus is something to check but you need to check it in combination with a visibility change. The HTML5 Visiblity API and this post about it helped me figure out a solution that is pretty solid except the mentioned browsers above because they have some issues with the navigator.msLaunchUri function and have their own approach implemented which doesn't rely on blur/focus. But the function is bugged and doesn't respond correctly all the time.

You can find my codepen here. Hopefully that helps you even though it is a bit late for an answer. This works for mobile browsers as well but I didn't test multiple yet worked for my Android 6.0.2. Might need some tweaks in the long run but I think it is pretty solid.

(function() {  var noProtocolHash = '#protocolXYnotsupported',      checkDelay = 800, // apps might start slowly      isBlurred = false,      inCheck = false,      inLauncherCheck = false,  tabVisible = (function(){       var stateKey,           eventKey,           keys = {                  hidden: "visibilitychange",                  webkitHidden: "webkitvisibilitychange",                  mozHidden: "mozvisibilitychange",                  msHidden: "msvisibilitychange"      };      for (stateKey in keys) {          if (stateKey in document) {              eventKey = keys[stateKey];              break;          }      }      return function(c) {          if (c) document.addEventListener(eventKey, c);          return !document[stateKey];      }  })(),  isMSIE = function(){    var rv = -1;    if(navigator.appName == 'Microsoft Internet Explorer'){      var ua = navigator.userAgent;      var re  = new RegExp("MSIE ([0-9]{1,}[\.0-9]{0,})");      if(re.exec(ua) != null){        rv = parseFloat(RegExp.$1);      }    }    else if(navigator.appName == 'Netscape'){      var ua = navigator.userAgent;      var re  = new RegExp("Trident/.*rv:([0-9]{1,}[\.0-9]{0,})");      if(re.exec(ua) != null){        rv = parseFloat(RegExp.$1);      }    }    return (rv !== -1)? true: false;  },  isEdge = function(){    return window.navigator.userAgent.indexOf("Edge") > -1;  },  checkIfFocusLost = function($el){    try {      document.location.href = $el.attr("href");    } catch (ex) {        document.location.href = document.location.href + '/' + noProtocolHash;    }    setTimeout(checkVisibility, checkDelay);  },  checkVisibility = function(){    if(tabVisible() && !isBlurred){      handleNoProtocol();    }    else {      handleProtocol();    }  },  handleNoProtocol = function(){    $('.result').text('has no protocol');    inLauncherCheck = false;  },  handleProtocol = function(){    $('.result').text('has the protocol');    inLauncherCheck = false;  },  checkHash = function(){    if(document.location.hash === noProtocolHash){      handleNoProtocol();    }  },  checkLauncherProtocol = function($el){    inLauncherCheck = true;    navigator.msLaunchUri($el.attr("href"), function(){      handleProtocol();    },     function(){      handleNoProtocol();    });    setTimeout(function(){      // fallback when edge is not responding correctly      if(inLauncherCheck === true){        handleNoProtocol();      }    }, 500);  },  checkIfHasProtocol = function($el){    inCheck = true;    if(isEdge() || isMSIE()){      checkLauncherProtocol($el);    }    else {      checkIfFocusLost($el)    }  };  checkHash();  tabVisible(function(){    if(tabVisible() && inCheck){      handleProtocol();      inCheck = false;    }      });  window.addEventListener("blur", function(){    isBlurred = true;     });  window.addEventListener("focus", function(){    isBlurred = false;     inCheck = false;  });  window.checkIfHasProtocol = checkIfHasProtocol;})();$('.protocol').click(function(e) {  checkIfHasProtocol($(this));  e.preventDefault();});

My code is tested with Win10: Chrome, Firefox, IE11, Edge + Android: Chrome (6.0.1)

there is also this github project https://github.com/ismailhabib/custom-protocol-detection which sorta has a similar approach maybe a little bit more maintained but i couldn't get their solution working for some reasons but maybe this is exactly what you need.

I think this might help you here with different browsers, but please define you question better or add at least some kinda example to make it clear.