Aadhaar is a 12-digit unique identity number issued to every resident of India by the Unique Identification Authority of India (UIDAI), a statutory authority established under the Aadhaar (Targeted Delivery of Financial and Other Subsidies, Benefits and Services) Act, 2016. The UIDAI was initially set up in January 2009 under the Planning Commission, with the goal of creating a single, foolproof identity system to eliminate duplicate identities and reduce leakage in the delivery of welfare schemes.
The system works by collecting an individual's demographic data and biometric data, which includes a photograph, ten fingerprints, and two iris scans, storing it in a centralized database. The core mechanism is outlined in Section 7 of the Aadhaar Act, 2016, which makes the number mandatory for receiving subsidies, benefits, and services funded from the Consolidated Fund of India. The UIDAI, which operates under the Ministry of Electronics and Information Technology, is responsible for assigning and authenticating these numbers. A key provision for data security is that core biometric information cannot be shared with anyone for any reason.
The legal framework was significantly shaped by the 2018 Supreme Court judgment in Justice K.S. Puttaswamy (Retd.) & Anr. v. Union of India & Ors., which upheld the constitutional validity of the Act but restricted its scope. The Court ruled that Aadhaar could not be made mandatory for services like opening bank accounts or obtaining mobile connections, and struck down Section 57 of the Act, which had allowed private entities to demand Aadhaar for identity verification. However, the Court upheld the mandatory linking of Aadhaar with PAN cards and its use for state subsidies under Section 7. A recent change, the Aadhaar (Authentication and Offline Verification) Amendment Regulations, 2025, legally recognized face authentication as a valid mode of verification, placing it on par with fingerprint and iris scans.