SAPUI5It is a JavaScript UI library consisting of a feature-rich core and a really large number of UI controls which are organized in a handful of libraries. The controls range from simple Button controls to complex ones like the sap.m.SplitContainer provide support for accessibility, keyboard navigation, touch interaction, right-to-left languages etc. out of the box. Different visual themes are available and can be adapted by either modifying the CSS or using the Theme Designer (a WYSIWYG tool). UI5 is based on jQuery, which can be directly used in UI5 applications, but there's a lot on top of it, so most of the time you might rather find yourself working with the controls. Many other Open Source libraries are used in UI5 and come bundled with it, e.g. LESS, the famous CSS processor, or datajs, the OData library.