Bootstrap is a free and open-source CSS framework directed at responsive, mobile-first front-end web development. It contains CSS- and (optionally) JavaScript-based design templates for typography, forms, buttons, navigation, and other interface components.
Bootstrap is the sixth-most-starred project on GitHub, with more than 135,000 stars, behind freeCodeCamp (almost 307,000 stars) and marginally behind Vue.js framework. According to Alexa Rank, Bootstrap is in the top-2000 in US while vuejs.org is in top-7000 in US.
Bootstrap 4
Mark Otto announced Bootstrap 4 on October 29, 2014. The first alpha version of Bootstrap 4 was released on August 19, 2015. The first beta version was released on 10 August 2017. Mark suspended work on Bootstrap 3 on September 6, 2016, to free up time to work on Bootstrap 4. Bootstrap 4 was finalized on January 18, 2018.
Significant changes include:
- Major rewrite of the code
- Replacing Less with Sass
- CSS Flexible Box support
- Dropping support for IE8, IE9, and iOS 6
- Adding responsive spacing and sizing utilities
- Dropping the Glyphicons icon font
- Improved form styling, buttons, drop-down menus, media objects and image classes
- Increasing global font size from 14px to 16px
- Huge number[quantify] of utility classes
