Rhyfel Byd 1914-1918 a’r profiad Cymreig / Welsh experience of the First World War 1914-1918 (www.cymru1914.org) is a mass digital archive of the primary sources relating to the First World War in Wales. It was funded by the UK’s Joint Information Systems Committee (JISC) from February 2012-October 2013. The project has digitized archives, manuscripts, photographs, art works, and oral histories held by the archives and special collections of Wales to create a coherent, consolidated digital collection revealing the often hidden history of the impact of the War: an invaluable resource for teaching, research, and public engagement that is available to support many aspects of the commemoration of the centenaries of the First World War. The Research Programme in Digital Collections at the National Library of Wales has carried out research into the use and impact of the digital collections of Wales, and these studies have identified key interventions in the digital life-cycle that can increase the impact of digital resources by a wide variety of stakeholders. The development of Cymru1914.org incorporated these findings. This presentation will discuss the development of this digital resource, and in particular, it will highlight ways that considerations of end-use and impact were built into project planning. This includes selection of content, interface development, community engagement, and planning for long-term sustainability of the finished digital resource. We will also discuss detailed analysis of the use of the resources since its launch in November 2013, in order to understand the full extent of the use and impact of the resource internationally.