How to Use the Aadhaar Checksum Validator

Type or paste a 12-digit Aadhaar number into the box above (spaces are fine — the tool strips them automatically).
Click Check. The tool verifies the number is 12 digits, doesn't start with 0 or 1, and passes the Verhoeff checksum used by UIDAI.
Read the result badge and the two-row decode table (the 11-digit identifier and its check digit).
Nothing you type ever leaves your device — the whole calculation runs as plain JavaScript in your browser tab, with no network request involved at any point.

Why Aadhaar Uses the Verhoeff Algorithm

Aadhaar is UIDAI's 12-digit unique identity number for Indian residents. The first 11 digits form the actual identifier; the 12th digit is a check digit computed with the Verhoeff algorithm, a checksum scheme published by Dutch mathematician Jacobus Verhoeff in 1969. UIDAI chose it specifically because, unlike a simple digit-sum check, Verhoeff mathematically guarantees detection of every single-digit error and every adjacent-digit transposition (swapping two neighboring digits) — exactly the two most common ways a human mistypes a 12-digit number.

The algorithm works by walking the digits right to left, applying a position-dependent permutation table to each digit, and combining the results using a custom (non-commutative) multiplication table. If the final combined value isn't zero, the checksum fails. It's deliberately not something you can verify by hand — that's part of the point, since a simple summing check would be easy to accidentally satisfy with a typo.

Worked Example

234123412346

passes both checks: it's 12 digits, starts with a valid leading digit (2), and its 12th digit (6) is exactly the Verhoeff check digit for the preceding 11 digits

23412341234

. Change that last digit to anything else — say

234123412347

— and the checksum fails immediately, even though the format still looks fine at a glance.

What This Tool Does NOT Do

This is a format and checksum validator only — a fast way to catch a typo before you submit a form, or to sanity-check a number you've copied from a photo. It does not connect to UIDAI's servers, does not perform eKYC or OTP verification, and cannot confirm the number is actually issued, active, or belongs to a real person. Passing this check only means the number is internally consistent by UIDAI's own error-detecting scheme.

Given how sensitive Aadhaar numbers are, this tool is built so your number is genuinely never transmitted anywhere — you can disconnect your network entirely after the page loads and the tool will keep working exactly the same.

Common Mistakes

Typing a leading 0 or 1 — UIDAI never issues Aadhaar numbers starting with those digits
Transposing two digits in the middle of the number — the Verhoeff check exists precisely to catch this
Confusing an Aadhaar number with an Aadhaar Enrolment ID (EID), which has a different, longer format
Assuming a checksum pass means the Aadhaar is currently active — UIDAI can deactivate numbers, and this tool has no way to know that

Frequently Asked Questions

Is my Aadhaar number safe to type here? Yes — this tool performs the entire calculation client-side in your browser. Nothing is uploaded, logged, or stored, and no network request is ever made with your number.

Does a valid Verhoeff checksum mean the Aadhaar is real? No. It means the number is internally consistent per UIDAI's own error-detection scheme — not that it's actually issued or active.

Why does UIDAI use Verhoeff instead of a simpler check like Luhn? Verhoeff catches both single-digit errors and adjacent transpositions; the classic Luhn algorithm (used for credit cards) misses some transposition errors.

Is this tool free? Yes, completely free, with no login and no usage limit.