Responsive Web Design Tester is a quick and easy way to test your responsive website.
Test your mobile site on different devices. This extension reflects both the size and the browser of the mobile device. Quickly preview your websites design at the dimensions they will be seen on popular devices. This extension also uses the correct User-Agent, but it does not render web pages in the same way as the mobile device. It is primarily for developers who want to test how a page responds to different devices. Supports both external and internal network (localhost). Add your own devices if you don´t find anything that suits your needs.