The UPSC syllabus differs significantly between the prelims and mains examinations. While the prelims mainly focus on general studies and includes the CSAT, the mains encompass a broader scope with detailed papers on various subjects, including General Studies, Essay writing, and Optional subjects. Prelims emphasize factual knowledge and current events, requiring strong analytical and reasoning skills, while mains demand in-depth understanding, application, and structured answer writing. Therefore, candidates must tailor their preparation strategies to address the specific requirements of each stage effectively.