the devil is in the detailthe specifics of something are the most problematic or important aspectThe proposal looks promising on paper, but the devil is in the detail of its implementation.NoteThe proposal looks promising on paper, but the devil is in the detail of its implementation.Elon.io is an online learning platformWe have an entire course teaching IELTS Vocabulary — Band 7+ grammar and vocabulary.Start learning IELTS Vocabulary — Band 7+ now