HttpListener Access Denied

Yes you can run HttpListener in non-admin mode. All you need to do is grant permissions to the particular URL. e.g.

netsh http add urlacl url=http://+:80/MyUri user=DOMAIN\user

Documentation is here.

Can I make it run without admin mode? if yes how? If not how can I make the app change to admin mode after start running?

You can't, it has to start with elevated privileges. You can restart it with the runas verb, which will prompt the user to switch to admin mode

static void RestartAsAdmin()
{
    var startInfo = new ProcessStartInfo("yourApp.exe") { Verb = "runas" };
    Process.Start(startInfo);
    Environment.Exit(0);
}

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EDIT: actually, that's not true; HttpListener can run without elevated privileges, but you need to give permission for the URL on which you want to listen. See Darrel Miller's answer for details.

If you use http://localhost:80/ as a prefix, you can listen to http requests with no need for Administrative privileges.

The syntax was wrong for me, you must include the quotes:

netsh http add urlacl url="http://+:4200/" user=everyone

otherwise I received "The parameter is incorrect"