Recs.
Updated
A toolkit providing simple and flexible HTML, CSS, and JS for popular UI components and interactions.
Specs
Pros
Pro Well documented
Documentation is thorough, well organized and full of live examples and templates ready for use. Every component and every part of the framework is explained and covered in depth.
Pro Custom builds
If you don't want to download the full Bootstrap framework. Custom builds of Bootstrap can be created, including only the desired CSS, CSS components, and JavaScript components. This can be done directly from the Bootstrap website by simply choosing what components to download.
Pro Easily make professional looking websites
Bootstrap makes it easy to learn how to make professional looking websites. It can even make code junkies semi-enjoy design.
Pro A wide variety of themes available
To help you avoid the "Bootstrap look", there are many resources that provide a great selection of themes and templates for Bootstrap.
Pro One of the most popular ones
Ranked on GitHub as the most starred CSS repository.
Cons
Con Large file size out of the box
Bootstrap has an out-of-the box filesize of ~276K, which is pretty large considering it's just CSS. Most of those styles aren't even used in 90% of web pages built with Bootstrap. By only including the required styles it can be trimmed by 70%-75%.
Con Too many classes
Bootstrap's over-reliance on HTML classes for styling can get very messy very quickly. There's also an overabundance of DOM elements which have a lot of classes and are more often than not nested inside DOM elements with even more classes. This gets problematic down the line because the maintainability of the project gets harder when the project starts to get large.
Con Websites can start to look the same
If the initial Bootstrap colors and styles are not changed or edited, different websites start looking the same even if they have nothing to do with each other and they are made by different developers.
Recommendations
Comments
Flagged Pros + Cons
Pro Builders
Builders available, such as Pingendo (https://pingendo.com/
) and Layoutit (https://www.layoutit.com/)