This paper focuses on a form of crowdsourcing that outsources ‘micro-tasks’ to virtual volunteers, within the context of a clearly defined Digital Humanities project contributing to preservation and research. The success of such projects relies on sufficient volunteer contributions over a period often limited by project budgets and resources. An understanding of website optimization can enable project teams to invite, instruct and incentivize ‘the crowd’ more effectively, and increase volunteer participation. Website optimization spans the disciplines of usability, human-computer interaction, and user-centred design, which are approaches traditionally used by web developers, designers, and online copywriters. With the rise of online collections, cross-disciplinary research and Digital Humanities, such boundaries are, often by necessity, rapidly dissolving; consequently, librarians, archivists, curators and Humanities scholars are using these approaches too. With a view to informing the planning, development and evaluation of future projects, this paper aims to give Digital Humanities project teams a deeper understanding of the main elements impacting on volunteer participation. It identifies a website optimization framework relevant to non-profit crowdsourcing, and demonstrates how it can be applied using the example of What’s on the Menu? a website developed by the New York Public Library.