A recent focus of design and building regulations, including form-based codes and the Leadership in Energy and Environmental Design for Neighborhood Development rating system, has been on promoting pedestrian activity. This study assessed perceptions of walkability for residential and commercial streetscapes with different design attributes in order to inform form-based regulations and codes that aim to impact walkability. We scored 424 images on four design attributes purported to influence walkability: variation in building height, variation in building plane, presence of ground-floor windows, and presence of a street focal point. We then presented the images to 45 adults, who were asked to rate the images for walkability. The results showed that perceived walkability varied according to the degree to which a particular design attribute was present, with the presence of ground-floor windows and a street focal point most consistently associated with a space's perceived walkability. Understanding if and which design attributes are most related to walkability could allow planners and developers to focus on the most salient built-environment features influencing physical activity, as well as provide empirical scientific evidence for form-based regulations and zoning codes aimed at impacting walkabilit.