Digital materials, the primary resources for the production of contemporary culture, have brought many challenges to the heritage sector in relation to their curation, conservation, and dissemination. Digital heritage sustainability involves practices that help ensure the maintenance, enrichment, and enjoyment of digital heritage resources over periods of time that span across generations. The digital heritage sustainability (DHS) framework presented in this article provides an analytic basis for understanding the challenges associated with the use of digital materials in museums and for assessing how digital heritage resources can be sustained over time. As an example of use, the framework is applied to the Museum of London's digital resources.