Institutional Repositories were first developed as an online solution for collecting, preserving, and disseminating the scholarship of universities, colleges, and other research institutions. The repository quickly evolved into a platform for libraries to publish and showcase the entire breadth of an institution’s scholarship including articles, books, theses, dissertations, and journals. Added support for images, video, audio, and other media has brought greater depth to repository collections. Since 2000, a number of repository platforms have been developed, each with their own set of benefits and technical criteria. Initially it was believed that repositories had to be open source and locally installed. The open source platforms offered unlimited flexibility for developers to build custom features and collections. However, over the past decade, the platforms have been enhanced to include many of the features that would previously have required local customization. Additionally, the potential high cost of ongoing development and maintenance of locally-hosted software has led many institutions to move to hosted options. The fear of lock-in associated with specific solutions has also faded due to the success of interoperability tools, such as OAI-PMH, available on each of the platforms. IR managers, sometimes on their second or third IR platform, can attest to the relative ease with which one can move from one platform to another. All of these changes put libraries exploring IRs for the first time in an enviable position. The products have richer feature sets, and all the major platforms are available as a hosted service, which arguably has a lower total cost of ownership and is less time-consuming than running an IR locally. Librarians are now truly free to compare platforms by focusing on the critical features that will address their needs and make their repositories successful. This guide compares the features of the major platforms and is intended to help libraries focus on which features will help facilitate the success of their repository. The comparison is divided into eleven categories to help librarians identify the features that are most important to building a successful institutional repository program at their institution.