Hi

UPSC main written exam consists of nine papers including 2 qualifying papers and seven papers calculated for ranking. Papers are:

Paper A: indian language ( compulsory)

Paper b : English

Paper 1: essay

Paper 2: indian heritage and culture, history and geography of the world and society

Paper 3: governance, constitution and welfare

Paper 4: technology, economic, development, agriculture, biodiversity, security and disaster management

Paper 5: ethics, integrity and aptitude

And the other 2 are optional subject papers

UPSC prelims subjects list are:

History

Geography

Civics/ political science

Economics

General science- physics, chemistry, biology

Environmental science

Sociology

For more information visit:

https://www.google.com/amp/s/competition.careers360.com/articles/upsc-ias-syllabus/amp

hope this helps