One of the greatest advantages of the YUI library is that it is flexible and light. With just 11 KB “on the wire,” it includes a suite for events, DOM normalizations, and language utilities. If you opt for the larger 17.4-KB size, it comes with all the core features, as well as the YUI Loader, which uses one request for CSS and another for JS to dynamically load the requirements for whatever YUI-based module you’re working with. None of the other market offerings can compete in terms of power or lightness.
The simplicity of the YUI Library belies in its power. It is a fantastic foundation for developing client-side applications. Each element of the YUI Library is scalable and adaptable, including the tools for creating widgets, managing objects, and customizing events.
One of the best things about the YUI Library is that it is built in modules, so you can pick and chooses the pieces you need for any given page. Many simple pages can get by with only the core package. If you work on a more complex project and need additional components, you can choose which ones to upload one at a time.
The BSD license is another great feature of the YUI Library, since all the widgets and utilities meet the same standards and share the same licensing requirements, even down to the testing and documentation. We are not aware of any other libraries that have a complete collection of widgets and utilities that can support all top browsers under a unified license. The YUI Library is also highly accessible, because the developers are committed to enhancing the experience for end users. The Library supports ARIA standards.
Finally, the YUI Library is packed with high-quality technical documentation, even for its newest release, YUI 3.x, the Carousel, and DataTable and other GA components. The engineers have posted handy cheat sheets, technical guides, and plentiful explanations and samples for developers to use.