Bootstrap 5 is the most popular CSS framework for building responsive, mobile-first websites. With its comprehensive suite of components and a powerful grid system, you can build beautiful UIs without writing tons of custom CSS.
The Grid System
Bootstrap uses a 12-column grid system. You can create flexible layouts using container, row, and col classes:
<div class="container">
<div class="row">
<div class="col-md-6">Left column</div>
<div class="col-md-6">Right column</div>
</div>
</div>Key Components
Bootstrap ships with dozens of ready-to-use components: Navbars, cards, modals, forms, buttons, alerts, and much more. All of them are customizable via CSS variables or Sass.
Utility Classes
Bootstrap 5 introduced a massive set of utility classes for spacing, typography, flexbox, and more — reducing the need for custom CSS significantly.