The concept of representation format, or type, permeates all technical areas of digital repositories. Policy and processing decisions regarding object ingest, storage, access, and preservation are frequently conditioned on a per-format basis. In order to achieve necessary operational efficiencies, repositories need to be able to automate these procedures to the fullest extent possible. JSTOR and the Harvard University Library are collaborating on a project to develop an extensible framework for format validation: JHOVE (pronounced “jove”), the JSTOR/Harvard Object Validation Environment. The initial release of JHOVE includes modules for arbitrary byte streams, ASCII and UTF-8 encoded text, GIF, JPEG2000, and JPEG, and TIFF images, AIFF and WAVE audio, PDF, HTML, and XML; and text and XML output handlers.