Despite the fact that technologies are commonly implemented in language classrooms and widely incorporated by students in their language learning, research on English learners' actual practices of technologies, especially the use outside the classroom, has been mostly limited. The aim of this study was to explore undergraduate English language learners' independent use and perceptions of mobile technologies for their foreign language writing, a productive skill that requires linguistic expertise in various aspects. Data were collected through a questionnaire from 305 English learners who enrolled in various English for Specific Purpose courses in a public university in Thailand. The findings indicated that the participants used various mobile technologies that mainly concerned with linguistic aspects of writing such as online dictionaries, machine translations, and language checker applications to support their foreign language writing. Their primary purposes of using technologies were to achieve accuracy, confidence and efficiency in their writing. This study sheds light on how mobile technologies play a supportive role and offer pedagogical potential in language learners' lives beyond the borders of classrooms.