It is often difficult for practitioners to trust analysis software if its methods are not transparent and welldocumented. The purpose of this paper is to open for review, comment and reference the methodology used within Sefaira to help those who use it and those who field requests to respond to its outputs. This paper will document the way in which Sefairaconducts cloud-based daylighting analysis to serve non specialist architect practitioners seeking to inform early-stage design decisions. This paper will explain how a Sefaira simulation is defined and conducted, with particular focus on the tool's unique use of cloud computing and how the tool is optimized to support early-stage decision making. This paper does not try to revalidate the Radiance or Daysim engines that Sefaira uses as its fundamental platform.