Which official websites like PIB and PRS are essential for current affairs for UPSC?

For authentic UPSC preparation, you should rely on these official sources rather than coaching notes alone. PIB is essential for daily government announcements and schemes, while PRS India provides critical analysis of Bills and Parliamentary reports.
For Socio-Economic data, NITI Aayog reports and the India Budget portal (for the Economic Survey) are vital. For specialized subjects, use the MEA for International Relations, MoEFCC for Environment, and IDSA for Internal Security.
These websites provide the official fodder and data needed to substantiating your Mains answers and build a balanced perspective for the Interview.