Methodological homogeneity in informal digital learning of English: A systematic review and roadmap for diversification

Research on informal digital learning of English (IDLE) has grown substantially, yet a systematic analysis of its methodological foundations is lacking. To map current practices, this methodological review examines 104 peer-reviewed studies (2015–2025) indexed in the Arts & Humanities Citation Index or the Social Sciences Citation Index . The findings reveal a dominant pattern of methodological homogeneity , characterized by heavy reliance on non-experimental designs (94.23%), self-report instruments (notably questionnaires; 69.49% of quantitative tools), and descriptive and correlational analyses (80.44% of quantitative analysis strategies). This profile is understandable, as the informal, nonlinear, and learner-driven nature of IDLE aligns naturally with exploratory approaches. However, this focus may limit the investigation of causal mechanisms and theoretical development. To support the field’s evolution, we propose a strategic diversification of methods. Integrating longitudinal designs to trace development, complementing self-reports with ethically collected and activity-sensitive behavioral and trace data, and leveraging new analytical tools such as learning analytics and, where appropriate, AI-assisted analysis can enrich inquiry and help build more robust, explanatory models of informal digital learning.