The Library of Congress is drafting a decision-support framework pertaining to the preservation of digital content. The framework is presented through a Web site that identifies and documents digital content formats that are promising (or unpromising) for long-term sustainability, together with some explanatory essays. The resource is intended to serve staff who evaluate born digital content for selection for the Library's collections and make provisions to sustain that content.The initial investigation has outlined two sets of high-level factors that may be used when choosing formats:• conceptual factors that may affect the sustainability of any digital format• factors that relate to quality or special functionality that might be desired for certain categories of content