INTRODUCTION: To evaluate the accuracy, reliability, and usability of Bend Ease, a novel smartphone-based digital health technology (DHT), which objectively self-measures spinal range of motion (SRoM) and remotely assesses morning stiffness. METHODS: This phase 1 study involved healthy volunteers (HV) and patients with axial spondyloarthritis (axSpA). Participants used Bend Ease by placing a phone against their chest during a forward-flexion bend, and the application collected and processed accelerometry data to measure bend angle in both clinical and at-home settings. Bend Ease measurements were compared to the video-based method (gold standard) and functional ability questionnaires. RESULTS: The study included 30 HV and 30 patients with axSpA. Bend Ease accurately measured forward-flexion bend angles, demonstrating strong correlation (r = 0.74) and concordance (ρ CONCLUSIONS: Bend Ease is an accurate, reliable, and user-friendly tool for assessing SRoM. As the first DHT to objectively evaluate morning stiffness upon waking, Bend Ease provides valuable assessments of spinal mobility when it is most impaired.