This study investigated the influence of students’ informal digital language on their formal academic writing. It focused on second year students in the Department of English Language and Literature, Alvan Ikoku Federal University of Education, Owerri. The study aimed to; (i) identify common features of informal digital language, (ii) examine their occurrence in academic essays, (iii) assess students’ awareness of register differences, (iv)determine the relationship between social media use and the transfer of informal language into formal writing. A mixed-methods research design was employed. It combined quantitative analysis of 180 academic essays with qualitative data from questionnaires and semi structured interviews involving 90 students. Findings revealed that students frequently use social media for extended periods, with 61.1% spending four hours or more daily, which reinforces habitual informal writing practices. Common digital language features included abbreviations, conversational tone, incomplete (fragmented) sentences, and nonstandard spellings. Analysis of academic essays indicated that 50% contained at least, one informal feature, with abbreviations and conversational tone being the most prevalent. A strong positive correlation (r = 0.68, p < 0.01) was observed between the frequency of social media use and the presence of informal features in academic writing. Although, students were generally aware of the differences between social media and academic writing, they often failed to regulate their language, particularly under time constraints. The study validates Halliday’s Register Theory. It demonstrates that language use is context dependent and influenced by habitual engagement with informal registers. The findings underscore the need for explicit instruction on register differentiation, integration of digital literacy into academic curricula, and institutional support through writing centers and workshops. Such interventions can enhance students’ academic writing competence and prepare them for effective communication in both academic and professional contexts.
Keywords: Academic writing, Informal digital language, Language transfer, Register awareness, Social media.