Studies suggested that emotion dysregulation and identity processes are involved in social media (SM) misuse, even if their proximal role has not been investigated. Previous studies rarely discriminated between specific activities or between types of SM. We recruited 50 young adults and implemented a momentary ecological assessment measurement. Four times by day, during seven days, we measured SM use, frequency of several activities on SM, emotion dysregulation, distress and clarity of self-concept. Daily time spent on Facebook, Instagram and TikTok were (...) retrieved from devices. Intradaily changes in emotion dysregulation and clarity of self-concept predict changes in SM addiction symptoms and frequency of use according to the type of activity. Daily changes in time spent on SM were not predicted by emotion dysregulation, distress and self-concept clarity. Findings suggest that emotion dysregulation and poor self-concept clarity are proximal risk factors for SM misuse. (shrink)