Abstract Language learning in the extramural digital (ED) context has recently gained momentum because it focuses on second language (L2) learners’ autonomous, unstructured, online learning activities beyond the classroom. Drawing upon Dörnyei’s L2 motivational self system (including the ideal L2 self, ought-to L2 self, and L2 learning experience) to operationalize L2 learners’ motivational mindsets, this study aims to investigate whether L2 English learners’ ought-to L2 self can be translated into their ideal L2 self and predict learning behaviors within the ED context. Survey data from 310 undergraduate students in a top-tier Chinese university were collected and analyzed following a structural equation modeling approach. The results indicate that participants’ ought-to L2 self can facilitate the development of their ideal L2 self only through the full mediation effect of the L2 learning experience in the ED environment. Also, while students’ ought-to L2 self cannot directly predict their motivated learning behaviors in the ED context, there exists a significant indirect impact through the joint mediation of the L2 learning experience and ideal L2 self. These findings contribute to the ongoing conversation about L2 motivational dynamics by unveiling the conversion and interaction of different L2 motivational forces in digital and out-of-class settings.