Digital technology enables parents and adolescents to communicate anywhere and anytime. Knowledge of parent-adolescent online communication, however, is mainly based on cross-sectional studies. In this preregistered 100-day diary study, 479 adolescents (Mage = 15.98, 54.9% girls; 96.9% Dutch) reported daily if they had communicated with their parents online, for how long (i.e., duration), and what they discussed (i.e., topics). Parent-adolescent online communication took place on 36% of days, for an average of 20 minutes a day, and predominantly concerned managerial topics. Five profiles of parent-adolescent online communication were identified, with most adolescents (55.4%) communicating infrequently and shortly. Although parents and adolescents can potentially be in contact throughout the whole day, only very few do so.