A carotid web (CaW) is a shelf-like, thin, triangular endoluminal projection typically arising from the posterior wall of the internal carotid artery (ICA) bulb. CaW is considered by many to be an intimal variant of fibromuscular dysplasia and is associated with an increased risk of ischemic stroke in otherwise low-risk, younger patients. The CaWY study is a cross-sectional, multicenter, population-based sonographic survey with blinded central image adjudication, reported in accordance with STROBE guidelines for cross-sectional studies, aimed at estimating the prevalence of CaW detected by duplex sonography in the general population aged 15-25 years.