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, how long (i.e., duration), and what they discussed (i.e., topics). Parent–adolescent online communication took place on 43% of days, for an average of 20 min a day, and predominantly concerned micro‐coordination. Five profiles of parent–adolescent online communication were identified, with most adolescents (55.4%) communicating relatively infrequently and briefly. Boys and younger adolescents communicated longer than girls and older adolescents. Although parent–adolescent online contact is possible all day, very few adolescents do so.