Hydra is a multi-institutional collaboration to build a common, open source framework for multi-function, multi-purpose, repository-powered applications. As symbolized by its name, Hydra's architecture reflects a "one body, many heads" design: a robust digital repository (the body) anchors feature-rich applications (the heads), tailored to content-, domain- and institution specific needs and workflows.

Hydra's technical framework features the Fedora Repository on the back end, with a front end comprising Ruby on Rails, Blacklight, solr, and a suite of web services. Hydra software is free and open source, available under an Apache 2 license.