Aadhaar is India’s national biometric identity system and the largest biometric database ever built. It is administered by the Unique Identification Authority of India (UIDAI), which was established by the Government of India in January 2009 and given a statutory footing by the Aadhaar Act of 2016. Each enrolled resident receives a unique 12-digit Aadhaar number linked to their biometrics.
Enrollment captures a substantial biometric record: ten fingerprints, two iris scans, and a facial photograph, tied to basic demographic details. That combination lets the system deduplicate at population scale - ensuring one person cannot hold two numbers - and lets services authenticate a person later by matching a fingerprint or iris against the stored record. Over the program’s life more than a billion residents have been enrolled, a scale no other identity system approaches.
Aadhaar’s purpose was to give a verifiable identity to hundreds of millions of people who lacked formal documentation, and to route government benefits and subsidies directly to them. It now underpins bank accounts, SIM cards, tax filing, and welfare delivery across India, with authentication transactions running into the billions.
The system has been the subject of intense debate over privacy, exclusion, and the risks of centralizing the biometrics of more than a billion people in one place. In a landmark 2018 judgment, India’s Supreme Court upheld Aadhaar’s constitutional validity for distributing government benefits while striking down requirements that private companies use it, and affirming a fundamental right to privacy. Aadhaar remains the defining real-world case study in what nationwide biometric identity makes possible - and what it puts at stake.