Doomscrolling refers to a unique media habit where social media users persistently attend to negative information in their newsfeeds about crises, disasters, and tragedies. Given the potential prevalence of this practice and its timely but chronic relevance for user experiences, political perceptions, well-being, and other outcomes, this project aimed to develop and validate a self-report measure of doomscrolling. Participant focus groups and an expert panel contributed to the refinement of an item bank, assessed in two survey studies for item structure, reliability, and construct validity. The item bank was tested with survey panelists across the Organisation for Economic Co-operation and Development; OECD (N = 401) to develop a unidimensional, 15-item scale with good reliability. Doomscrolling was less prevalent than anticipated, but variable. Tests of validity with survey panelists (N = 502) indicated that doomscrolling can be considered a distinct concept, and that it was closely related to online vigilance, problematic use of the internet and social media, and fear of missing out (FOMO). Doomscrolling was also linked to passive social media use, habitual media use, anxiety, poor self-control, and several personality traits. Men, younger adults, and the political-engaged were more likely to engage in doomscrolling.