Informal Digital Learning of English (IDLE) is the result of the affordances of technology that allow learning to take place in unstructured learning contexts. However, how IDLE facilitates students' English language learning remains unclear. This study aims to investigate the strategies English as a foreign language (EFL) students employ to learn English knowledge while doing IDLE, as well as how they practice the knowledge to improve their mastery of the English language. This study employed a phenomenology approach and recruited 16 participants from an Indonesian state university to better comprehend their experiences with IDLE. The researchers employed semi-structured interviews and inductive thematic analysis to examine the data. The findings revealed that EFL students employed various strategies in a variety of online and offline activities as found in formal learning while doing IDLE, primarily to remember linguistic features such as vocabulary, phrases, expressions, and pronunciation. In addition, they participated in such activities to improve their communication and writing skills only. Four implications of conducting IDLE to promote English language learning success are also discussed.