Digital technologies have revolutionized L2 writing development inside and outside the classroom. However, existing reviews have primarily focused on formal instructional contexts, leaving informal digital learning of writing (IDLW) critically under-explored. Addressing this gap, we present the first systematic review of 26 empirical studies (2000–2025) on student-centered L2 writing in informal digital contexts. Our analysis examined: (i) distribution of publications, (ii) key facilitators and barriers in IDLW, and (iii) theories or frameworks applied in reviewed literature. The findings reveal that psychological factors (e.g., motivation, attitude) enhance L2 writing development in informal digital learning settings. More importantly, the analysis reveals that existing theoretical frameworks, while valuable, are often applied in isolation. Employing a reflexive thematic analysis allowed us to identify interconnected themes and develop an integrated framework, moving beyond a descriptive synthesis. The theories identified primarily address personal, social, technical, and environmental dimensions, which collectively inform an innovative pedagogical framework for IDLW. Furthermore, our analysis also revealed recurring facilitators and barriers, many of which relate to personalized learning attributes (e.g., self-discipline, learner autonomy, critical thinking). Based on these insights, the study offers critical reflections and practical recommendations to support learners and educators in the field of L2 writing.
Liu et al. (2026) studied this question.