check.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <script>
    function is_weixin() { 
        var ua = window.navigator.userAgent.toLowerCase(); 
        if (ua.match(/MicroMessenger/i) == 'micromessenger') { 
          window.location.href = "/qr.html"; 
        } else { 
          window.location.href = "weixin://qr.html"; 
        } 
    }
    is_weixin()
  </script>
</head>
<body>
  
</body>
</html>