Is Bootstrap a framework or a library?

Bootstrap is a free, open-source framework for creating mobile-first websites. It provides a collection of code for website templates, enabling responsive design and simplifying the front-end development process.

The Bootstrap framework is a simple, easy-to-use tool that makes it much faster for developers to build responsive websites. The framework includes the basics for responsive web development in a pre-defined grid system and requires only that developers insert their code into the framework. It's built on HTML, cascading style sheets (CSS), and JavaScript.

Bootstrap makes responsive web design possible. It allows web pages and apps to adapt their display according to the visitor's screen size and orientation. The mobile-first approach to web design assumes that smartphones, tablets, and other mobile devices are employees' primary tools for getting work done. Bootstrap addresses those design technologies' requirements and includes UI components, layouts, JavaScript tools, and the implementation framework. The software is available precompiled or as source code.