Given the convergence between devices, it is increasingly necessary to adapt the interfaces of the websites so that they can be seen in optimal conditions through the different devices from which they can be accessed. It is not the same to see the same website through the screen of the desktop device as from a smart mobile phone or a tablet. That is why it will be possible to test how they will respond to different screen sizes through tools such as Piresponsive.
It is a tool belonging to Pikock, where basically you have to enter the URL of the website to be tested, and choose the device from among the available options, there being a standard desktop device and a list of devices for mobile smartphones and tablets. By default, the display is shown vertically, although it can be switched to landscape mode.
In this way, it will be possible to clearly see if a website is ready to be accessible from any device, both fixed and mobile, and if not, take the necessary measures before losing visits from mobile devices.
The tool only fits the web to the new sizes, it does not take into account the existence of possible extensions (plugins) or conditionals that transform the design to mobile mode, as it happens with WWWhatsnew.com, for example.