In the mid-2000s, developers of integrated library systems and indexing and abstracting services began to create a next-generation system that would provide an alternative to the Z39.50 federated search process. Web-scale discovery harvests metadata and often full-text content from a variety of information sources, such as library catalogs, commercial databases, and local library digital repositories. This technology offers users a simple search interface and single (and, in most cases, faceted) results lists. What sets discovery services apart from federated search is in their creation of a centralized index of content across sources and platforms, which allows for a faster retrieval process (Vaughan, 2011e). Discovery tools can offer the “Google generation” an experience similar to a Google search with a broad range of academic sources. In recent years, several products, both proprietary and open-source, have emerged, including the four studied here: EBSCO Discovery Service (EDS)™, Innovative Interface’s Encore™, Ex Libris’ Primo®, and Serials Solutions®’ Summon™.