<!DOCTYPE html>
<html>
<body>
<p>Click the button to display the user-agent header sent by the browser to the server.</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
var x = "User-agent header sent: " + navigator.userAgent;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>