Aadhaar is the world's largest biometric identity system with approximately 134 crore live Aadhaar holders

• Aadhaar = 12-digit unique identity number issued by UIDAI (Unique Identification Authority of India) using demographic + biometric data (fingerprint, iris, face).
• World's largest biometric ID system with ~134 crore live Aadhaar holders and >17,000 crore authentication transactions completed.
• Backbone of India's Digital Public Infrastructure (DPI) — enables DBT, JAM trinity, e-KYC, subsidy delivery.
• High UPSC salience: cuts across GS-II (governance, rights, SC judgments), GS-III (digital economy, cybersecurity) and ethics (privacy).