•UV–vis spectroscopy was used for grape-must caramel quantification in vinegars.•Balsamic and PDO vinegars’ grape-must caramel content was predicted.•Univariate and multivariate calibration approaches were assessed and compared.•Prediction results were compared with those obtained by other spectroscopies.•The results encourage UV–vis as an alternative tool for monitoring caramel addition. The addition of E-150d caramel, known as grape-must caramel in vinegars, is a legal but without limitation practice in Spanish wine vinegars, as those with a protected designation of origin (PDO), for unifying the final colour of different batches and barrels. It is also used in the production of ‘Balsamic vinegar of Modena’ vinegars, with a maximum addition fixed at 2% v/v by law. Although its quantification in vinegars was studied by other techniques, there is still not any official method for it. Therefore, UV–vis spectroscopy was assessed as a quick analytical method able to quantify grape-must caramel in Balsamic vinegars of Modena and Spanish PDO wine vinegars. Univariate and multivariate calibrations were assessed for this quantification. Results demonstrated the ability of UV–vis spectroscopy coupled with multivariate calibration in the quantification of grape-must caramel, predicting caramel amounts under 2% v/v in both Balsamic and PDO wine vinegars.