The essence of mobile learning is learners' agentic use of mobile devices to create learning experiences across time and space. Thus, understanding learners' perceptions and preferred use of mobile devices for learning are critical to realizing the educational potentials of mobile learning. This study explored language learners' self-directed use of mobile devices beyond the classroom through a survey and interview study with foreign language learners at a university in Hong Kong. A total of 256 learners were surveyed and 18 were interviewed to understand the nature of mobile language learning experiences that these learners engaged in autonomously beyond the classroom. Exploratory factor analysis yielded three dimensions of self-directed out-of-class mobile learning experience. Among the three dimensions, learners were found to use mobile devices more for facilitating the personalization of learning than for enhancing the authenticity and social connection in learning. This study further revealed that selective use was an outcome of the interaction between learner-defined affordances of the devices, their culturally informed and habitual use of the devices, their perceptions of the nature of the learning tasks, and the tempo-spatial circumstances of task implementation. The findings suggest that these factors need to be considered when designing mobile learning activities and educational interventions that promote mobile learning beyond the classroom.