Bootstrap UI is an open-source front-end development framework for creating responsive, mobile-first web interfaces. It is a library of HTML, CSS and JavaScript components that are used to build user interfaces. With Bootstrap UI, developers can quickly create prototypes or production ready web pages with minimal effort. It is highly customisable and easily extensible allowing developers to alter the look and feel of their projects. Bootstrap UI also includes powerful tools for developing modern user experiences by incorporating common components such as navigation bars, tables, forms and buttons. The framework also supports the latest technologies such as HTML5, CSS3 and JavaScript so developers can create projects that are up-to-date with the latest standards. By utilising Bootstrap UI's features, developers can focus on building great user experiences while still having access to robust development tools.