Libraries increasingly offer much of their collection online, rendering it invisible or unavailable to readers who, for reasons of information experience, prefer to browse the shelves. Although the evidence that shelf browsing is an important part of information behavior is increasing, information browsing as a behavior is somewhat of a black box (in contrast to web browsing, which is relatively well understood). It seems likely from early work that browsing is not, in fact, a monolithic behavior, but rather a set of behaviors and goals. The typologies presented in these works, however, are of a too high level to offer much insight into what support is needed for successful online browsing. In contrast, a recent spate of speculative browsing technologies meet some browsing needs, but offer little theoretical understanding of how systems support browsing. The major contribution of this article is a new typology of library browsing behavior based on recent observations of browsing behavior in libraries. The secondary contribution is an understanding of the interface features that would support these types of information browsers in an online environment.