The associations between disease activity and several clinical signs in vitiligo have been described, but a widely accepted and validated scoring system is lacking. To validate the Vitiligo Signs of Activity Score (VSAS) for physicians. Three visible clinical signs were scored on 15 body locations: confetti-like depigmentation (c), Koebner phenomenon (k) and hypochromic areas/borders (h). The inter- and intrarater reliability of the global VSAS and VSAS subscores (c-VSAS, k-VSAS and h-VSAS) were tested by four and three raters (physicians), respectively. Construct validity and feasibility were evaluated. The VSAS demonstrated good inter-rater reliability, with an intraclass correlation coefficient (ICC) of 0·87 in the first round and 0·90 in the second round. The intrarater reliability ICCs were all ≥ 0·86. The inter-rater reliabilities of the subscores were excellent for c-VSAS and fair for k-VSAS and h-VSAS (ICC 0·83, 0·51 and 0·53, respectively, in the first round). Evidence for construct validity was provided. The completion time by the raters (median 2·18 min per patient) improved during the second round (median 1·33 min per patient). A limitation of the study is the low number of patients, mainly of skin phototypes II-III, from a single tertiary centre. The VSAS appears to be a valid and reliable instrument to score visible clinical signs linked to disease activity in a standardized way. What is already known about this topic? Evidence exists for a possible link between several visible clinical signs in vitiligo and disease activity. A widely accepted and validated scoring system to quantify these clinical signs is lacking. What does this study add? The Vitiligo Signs of Activity Score (VSAS) underwent preliminary validation and may assist quantification of visible clinical signs linked to disease activity in a standardized way in clinical practice and trials. What are the clinical implications of this work? VSAS may be used for future trials that aim to establish the clinical significance of the specific visible clinical signs in vitiligo in a more controlled setting. Linked Comment: Eleftheriadou. Br J Dermatol 2020; 183:801-802. © 2020 The Authors. British Journal of Dermatology published by John Wiley & Sons Ltd on behalf of British Association of Dermatologists.