While you can write custom CSS to accomplish nearly any look you want for your webpages, many developers prefer to use a pre-written CSS library that provides rules covering many common user interface needs. For example, CSS-based menus are very challenging to write well, but a well-designed library makes the task very approachable. CSS libraries also provide a consistent UI look and feel across websites, which helps people browsing your website quickly identify how to move around.
One of the most popular CSS frameworks is Bootstrap , which is used by thousands of websites. Other popular CSS libraries include Tailwind , Semantic , and Animate which as the name suggests provides animation components.