A 12-digit biometric identity number issued since 2010 to about 1.38 billion residents of India and used for welfare, banking and tax. It was placed on a statutory basis in 2016 and upheld with limits by the Supreme Court in 2018, after the 2017 Puttaswamy ruling declared privacy a fundamental right.
Aadhaar is India's biometric digital identity system: a 12-digit number issued to residents after the collection of demographic data, ten fingerprints, both irises and a photograph. The Unique Identification Authority of India (UIDAI) was created by an executive notification of the Planning Commission on 28 January 2009, with the Infosys co-founder Nandan Nilekani as its first chair. The first numbers were issued in September 2010. By July 2018 about 1.22 billion people were enrolled, and by October 2024 there were about 1.38 billion Aadhaar holders, making it the largest biometric identity system in the world.
Aadhaar was presented as a way to give every resident a portable proof of identity, remove duplicate and fictitious beneficiaries from welfare rolls and enable direct transfers to bank accounts. It became the base layer of "India Stack", which also includes electronic know-your-customer checks and the UPI payments system.
For its first years Aadhaar operated without a statute. Parliament passed the Aadhaar (Targeted Delivery of Financial and Other Subsidies, Benefits and Services) Act in March 2016. The government introduced it as a Money Bill, which limited the role of the upper house, the Rajya Sabha; opposition parties objected. UIDAI became a statutory authority under the Act.
Use of Aadhaar is governed by UIDAI regulations and by the ministries and agencies that require it. Authentication works by sending a number with biometric or one-time-password data to UIDAI's central servers, which reply yes or no. Face authentication was added as a mode in 2018.
Courts. Litigation began in 2012. In August 2017 a nine-judge bench of the Supreme Court in Justice K.S. Puttaswamy (Retd.) v. Union of India unanimously held that privacy is a fundamental right. In September 2018 a five-judge bench upheld the Aadhaar Act by a 4 to 1 majority, permitting mandatory Aadhaar for welfare benefits and income-tax filing, but struck down section 57, which had allowed private companies to require Aadhaar, so that banks, schools and mobile operators could no longer make it a condition of service. Justice D.Y. Chandrachud dissented, holding the Act unconstitutional, including its passage as a Money Bill. The Aadhaar and Other Laws (Amendment) Act 2019, which received presidential assent on 23 July 2019, allows holders to use Aadhaar voluntarily for authentication or offline verification and amends the telegraph and anti-money-laundering laws so that telecom licensees and banks can use it to verify customers.
Aadhaar is publicly financed infrastructure. Governments have claimed large savings from removing duplicate beneficiaries: in 2016 the finance minister cited ₹150 billion across schemes. Independent analysts disputed such figures: against the petroleum ministry's claim of ₹14,672 crore saved on cooking-gas subsidies in 2014/15, an IISD policy brief by Kieran Clarke (2016) put the maximum gross saving from Aadhaar-based deduplication that year at about ₹12 to 14 crore. Aadhaar has enabled direct benefit transfers and very low-cost identity checks for financial inclusion, and it is used by hundreds of millions of people every month.
Exclusion. When biometric authentication became mandatory in rations distribution, failures caused by poor connectivity, worn fingerprints or data errors denied food to eligible households. A large randomised and natural-experiment study in Jharkhand by Muralidharan, Niehaus and Sukhtankar found that stricter biometric requirements reduced leakage but that between 1.5 and 2 million legitimate beneficiaries lost benefits at some point, mostly because of how the transition was managed. An earlier study of biometric smartcards in Andhra Pradesh found faster and less corrupt payments, which shows that design and implementation matter as much as technology.
Security and surveillance. In 2017 researchers reported Aadhaar data exposed on government websites. In January 2018 The Tribune reported that its journalists had bought access to the database for ₹500; UIDAI denied a breach and filed a complaint against the newspaper. Civil-liberties groups argue that a single identifier linked to bank accounts, phones and welfare enables profiling; the dissent in the 2018 judgment made the same argument. Oversight of UIDAI by an independent data-protection authority was absent for years.
Aadhaar achieved near-universal coverage of the adult population and became infrastructure for payments, welfare and private services. Its record on welfare efficiency is mixed and contested, and its exclusion costs fell on the poorest. Its constitutional history produced one of the most important privacy judgments in the world.
Near-universal enrolment (about 1.38 billion holders by October 2024) and use as infrastructure for direct benefit transfers, banking and identity checks. Savings claims are contested; biometric requirements excluded legitimate beneficiaries in some programmes. The Supreme Court upheld the Aadhaar Act in 2018 but barred private companies from requiring it under section 57.
In 2018 the Supreme Court of India upheld the Aadhaar Act by a 4 to 1 majority but struck down section 57, so private entities may not require Aadhaar as a condition of service; Justice Chandrachud dissented.[1][2]
In 2017 a nine-judge bench of the Supreme Court of India unanimously held that privacy is a fundamental right protected by the Constitution.[1]
Muralidharan, Niehaus and Sukhtankar found that stricter biometric verification in a major Indian welfare programme reduced leakage, but 1.5 to 2 million legitimate beneficiaries lost benefits at some point, mostly because of how the transition was managed.[1][2]
Official savings claims for Aadhaar-linked transfers are contested: against a claimed ₹14,672 crore saved on cooking-gas subsidies in 2014/15, an IISD analysis put the maximum gross saving from Aadhaar-based deduplication at about ₹12-14 crore.[1][2]