With the recent surge of mobile users accessing the internet from anywhere, it is increasingly important to develop mobile-friendly websites. In order to do this, it is essential to first test your mobile pages against specific user agents. In other words, it is a must to detect the web browser that a particular user is using. This task can be quite difficult if you are not an expert in such matters. However, with the help of Responsive Tester, you can do just that. This is an application that allows you to test your web pages against the user agent that is being used.