The subjects compulsory for the UPSC Mains examination include English and Indian Language, along with an Essay paper. Additionally, candidates must choose from a set of optional subjects based on their interests and proficiency. The remaining papers cover various domains, including General Studies (I, II, III, and IV) that encompass diverse areas such as history, polity, geography, economy, and ethics. This combination ensures a well-rounded evaluation of the candidates' knowledge and skills across critical facets of governance.