uses
Posix.Stdlib;

procedure TForm1.btnStartClick(Sender: TObject);
begin
  _system(PAnsiChar('open http://127.0.0.1:8001'));
end;

uses
  Apple.Utils;

procedure TForm2.btnStartClick(Sender: TObject);
begin
  SharedApplication.openURL(StringToNSURL('http://www.embarcadero.com'));
end;

uses
  Androidapi.JNI.GraphicsContentViewText,
  FMX.Helpers.Android;
procedure TForm2.btnStartClick(Sender: TObject);
var
  intent: JIntent;
begin
  intent := TJIntent.JavaClass.init(TJIntent.JavaClass.ACTION_VIEW,
    TJnet_Uri.JavaClass.parse(StringToJString(TIdURI.URLEncode(URL))));
  try
    SharedActivity.startActivity(intent);
    exit(true);
  except
    on e: Exception do
    begin
      if DisplayError then
        ShowMessage('Error: ' + e.Message);
      exit(False);
    end;
  end;
end;