How is an Aadhaar number validated?

An Aadhaar is 12 digits. UIDAI's structural rules require the first digit to be 2–9 (it can never be 0 or 1), and the 12th digit is a Verhoeff check digit computed over all 12 digits using the dihedral-group multiplication, permutation and inverse tables. A number passes when the running Verhoeff checksum resolves to 0.

Does a valid format mean the Aadhaar is registered to someone?

No. The Verhoeff checksum only confirms the number is mathematically well-formed. It cannot tell you whether the Aadhaar was actually issued or who holds it, and this tool never contacts the UIDAI database.

What is the Verhoeff checksum?

The Verhoeff algorithm is a checksum based on the dihedral group D5. It multiplies a permuted version of each digit together using a fixed multiplication table; a valid number leaves a running product of 0. It catches all single-digit errors and most adjacent transpositions, which is why UIDAI uses it for Aadhaar.

Can an Aadhaar number start with 0 or 1?

No. By UIDAI design the first digit of a valid 12-digit Aadhaar is always 2 through 9, so any number beginning with 0 or 1 is invalid regardless of its checksum.

Does the validator accept spaces or dashes?

Yes. Aadhaar is commonly written in groups of four (e.g. 2345 6789 0123). The validator strips spaces before checking, so formatted and unformatted input both work.

Is my Aadhaar number sent anywhere?

No. The validator is privacy-first. The first-digit rule and Verhoeff check run locally in your browser with JavaScript — there are no network requests and your Aadhaar number never leaves your device.

India Aadhaar Format Validator — Verhoeff Checksum Check

India Aadhaar format validator

Check whether an Indian Aadhaar number follows UIDAI’s published structure. This is useful for developers building form validation, data-entry teams catching typos before submission, and anyone wanting to confirm a number is well-formed — without ever contacting a government database.

How it works

The validator runs two checks on the 12-digit number:

First-digit rule: the leading digit must be 2–9. UIDAI never issues Aadhaar numbers starting with 0 or 1.
Verhoeff check digit: the 12th digit is a checksum computed over all 12 digits using the Verhoeff algorithm’s dihedral-group multiplication (d), permutation (p) and inverse tables. Processing the digits right-to-left, a valid number leaves a running product of 0.

A valid format passes both checks. The breakdown shows each result separately so you can see exactly why a number passes or fails.

Example

Number	First digit 2-9?	Verhoeff = 0?	Result
2345 6789 0124	Yes	Yes	Valid format
1234 5678 9012	No (starts with 1)	—	Invalid
2345 6789 0123	Yes	No	Invalid checksum

A valid format only means the number is mathematically well-formed — it does not prove the Aadhaar was issued or who holds it.

Privacy-first: every check runs in your browser. Nothing is uploaded, stored or sent to any server, and this tool does not query the UIDAI database.