As research into online informal language learning (OILL) develops as a field, the impact on such practices for a wide variety of contexts can be considered. In the case of this publication, the study abroad (SA) context is of particular interest. Indeed the study abroad student may interact with a range of online learning resources in formal, non-formal and informal contexts before during and after mobility. This review article looks at both Online Informal Language Learning and non-formal learning activities relevant to SA, with particular focus on the Erasmus + online learning support (OLS) platform and popular commercial non-formal learning apps such as Duolingo and Busuu. Such informal and non-formal learning activities also interact with formal language learning offered to SA students, some of which may also take place online. Formal, non-formal and informal learning can therefore be seen to constitute a personal learning environment (PLE) which is specific to each learner. Complex systems views of language learning, including usage based approaches and cognitive grammar, form a useful theoretical framework for understanding how second language (L2) skills may develop as learners are exposed to frequently occurring prototypes in salient contexts in input. While it is now widely accepted that such exposure has a significant impact on comprehension levels, research continues into individual differences between learners in terms of exposure time and cognitive, affective and linguistic engagement with the target materials. Data will be presented indicating that while formal and non-formal learning activities involve exposure times which are often insufficient for significant language development when taken in isolation, informal learning activities offer exposure times and forms of engagement which support language development for many learners. Issues surrounding the assessment and certification of linguistic skills gained outside the classroom are addressed in conclusion.