WebJars is an easy way for server-side developers (such as your humble servant) to manage client-side resources such as Bootstrap, jQuery and their like, within the same package management tool they use for their server-side libraries. In essence, what WebJars does is package a set version of the client-side resource (CSS or JavaScript) in the META-INF/resources of a JAR and upload it on Maven Central. Then, any Java EE compatible web-container makes the resource available under a static URL.