Identity formation is one of the key developmental tasks in adolescence. According to Erikson (1968) experiencing identity uncertainty is normative in adolescence. However, empirical studies investigating identity uncertainty on a daily basis are lacking. Hence, studying individual differences in daily certainty (i.e., identity commitment levels) and uncertainty (i.e., identity commitment fluctuations and identity reconsideration) in the identity formation process may advance our knowledge about the extent to which adolescents' identity uncertainty is part of normative identity development. Therefore, this longitudinal study examined heterogeneity in certainty and uncertainty dynamics of adolescents' daily identity formation using a longitudinal microlevel approach. Dutch adolescents (N = 494; M[subscript age] = 13.03 years at T1; 56.7% boys) reported on 2 key dimensions of identity formation (i.e., commitment and reconsideration) in both the educational and interpersonal domain on a daily basis for 3 weeks within 1 year, across 5 successive years. Multivariate latent class growth analyses suggested both in the educational and interpersonal identity domain a class of adolescents displaying a "crisis-like" identity formation process, and an "identity synthesis" class. Classes revealed differential development of (global and school) anxiety, aggression, and best friend support. Taken together, the present study confirmed Erikson's notion that experiencing daily identity uncertainty is common during adolescence. However, a substantial amount of adolescents also showed a process toward identity maturation already during adolescence.