Bootstrap is a free and open source front end development framework for developing websites and web applications. It is the most popular HTML, CSS, and JavaScript framework for building responsive, mobile-first websites.

Responsive design allows a web page or an application to detect user’s screen size as well as orientation and automatically adapt the different display accordingly. The mobile first approach presumes that smartphones, tablets and task-specific mobile applications are employees’ primary tools for getting work done and fulfills the need of those technologies in design.