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Aadhaar Format Validator

100% Free

Validate a 12-digit Aadhaar number's format using the Verhoeff checksum — instant, client-side, format-only.

Verhoeff Algorithm
100% Client-Side
Instant
No Data Stored
1

Enter Aadhaar Number

Type or paste a 12-digit Aadhaar — spaces and dashes are OK.

Privacy: Validation runs entirely in your browser. Your Aadhaar number is never sent to a server, stored, or logged.

2

Validation Result

Enter a 12-digit Aadhaar number

Validation Checks

Length is exactly 12 digits·
Contains digits only (0–9)·
First digit is between 2 and 9·
Verhoeff checksum passes·

This is a format-only check. It does not query UIDAI and cannot confirm whether an Aadhaar has been actually issued to a real person.

100% client-side — nothing leaves your browser.
No network call, no logging, no analytics on your Aadhaar number.

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<iframe
  src="https://tools.town/embed/aadhaar-format-validator/"
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  style="border:none; border-radius:12px;"
  loading="lazy"
  title="Aadhaar Format Validator">
</iframe>

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How to Use

  1. 1 Paste or type your 12-digit Aadhaar number into the input box — spaces and dashes are accepted
  2. 2 The tool instantly checks length, digit-only content, the UIDAI first-digit rule (2–9), and the Verhoeff checksum
  3. 3 Read the verdict card at the top of the result panel — green for valid, red for invalid with the exact reason
  4. 4 Use the per-rule checklist to see which check passed or failed
  5. 5 If valid, copy the cleanly formatted number (XXXX XXXX XXXX) with the Copy button

Features

  • Implements the official UIDAI Verhoeff checksum used to validate Aadhaar numbers
  • Accepts input with or without spaces, dashes, or extra whitespace — auto-cleaned
  • Shows a per-rule validation checklist so you know exactly what failed
  • Enforces the UIDAI rule that the first digit must be 2–9 (0 and 1 are reserved)
  • Formats valid numbers as XXXX XXXX XXXX with one-click copy
  • 100% browser-based — your Aadhaar is never sent to any server, stored, or logged

Why it Matters

Aadhaar is India's most-used identity document — and a single mistyped digit silently corrupts KYC forms, eKYC payloads, and bank onboarding flows. A format check catches typos and OCR errors before they hit a real API. The Verhoeff algorithm is the same self-checking math UIDAI itself uses to detect the most common entry mistakes (transposed digits, single-digit slips). This tool runs that exact check entirely in your browser.

★★★★★

Use Cases

KYC Form Pre-Validation

Catch typos before submitting Aadhaar in onboarding forms or eKYC flows

HR & Payroll Bulk Checks

Quickly verify employee Aadhaar formats before importing into HRMS

Developer Test Fixtures

Generate or verify mock Aadhaar numbers for staging without touching real data

Compliance Spot-Check

A privacy-safe second opinion when reviewing a customer-submitted form

How this validator works

This tool runs four sequential checks against any Aadhaar number you enter. All four must pass for the verdict to be Valid.

  1. Length. After stripping spaces and dashes, the number must be exactly 12 digits.
  2. Digits only. No letters, no symbols — only 0–9.
  3. First-digit rule. UIDAI never issues a citizen Aadhaar starting with 0 or 1, so the first digit must be 2–9.
  4. Verhoeff checksum. The 12th digit is a check digit computed from the other 11 using the Verhoeff algorithm. If a single digit is mistyped or two adjacent digits are swapped, the checksum will fail — which is how UIDAI’s systems catch typos at point-of-entry.

If any one of these fails, the verdict turns red and the per-rule checklist below it shows you exactly which rule broke.

What this validator does NOT do

This is a format check, not an identity check. Specifically, it does not:

  • Contact UIDAI’s servers or verify against the Aadhaar database.
  • Confirm whether the number has actually been issued to a real person.
  • Tell you anything about the person the Aadhaar belongs to.

A 12-digit number that passes all four checks here is mathematically consistent — meaning it could be a real Aadhaar. But there are billions of mathematically consistent 12-digit numbers, and only ~1.4 billion actual Aadhaars. Always pair this check with a real eKYC flow before trusting an Aadhaar in production.

Privacy

Every check happens in your browser via a pure JavaScript function (validateAadhaar in our open-source src/tools/validators/aadhaar.ts). The page does not send your Aadhaar over the network, store it in localStorage, or include it in any analytics event. You can verify this yourself by opening the Network tab of your browser’s developer tools — typing into the input produces zero outbound requests.

Frequently Asked Questions

Does this validator confirm an Aadhaar is real or actually issued?
No. This is a format-only check. It verifies the 12 digits are internally consistent (length, digit-only, UIDAI first-digit rule, Verhoeff checksum). Only UIDAI itself can confirm whether an Aadhaar has been issued to a real person. Always treat a 'valid' result here as 'passes basic structural checks', not as identity verification.
Is my Aadhaar number sent to any server?
No. Validation runs entirely in your browser using JavaScript. The number never leaves your device — no network call, no logging, no analytics. You can verify this by opening your browser's Network tab while validating.
What is the Verhoeff algorithm?
Verhoeff is a checksum algorithm that detects all single-digit errors and most digit-transposition errors — the two most common typing mistakes. UIDAI uses it as the 12th digit of every Aadhaar. If a single digit is mistyped, the checksum will fail.
Why must the first digit be 2–9?
UIDAI reserves the leading digits 0 and 1 for internal/system numbers and never issues a citizen Aadhaar starting with them. So any 12-digit number beginning with 0 or 1, even if it passes the Verhoeff check, is not a valid issued Aadhaar.
Can I use the example button on a production form?
No. The example number (234567890124) is a synthetic test fixture — it passes the Verhoeff check but is not an issued Aadhaar. Use it only for testing your own forms or this validator.
📖

Want to understand the math?

Browse all guides →
Verhoeff Algorithm Explained
aadhaar

Verhoeff Algorithm Explained: How Aadhaar Detects Typos

The 12th digit of every Aadhaar number is a Verhoeff check digit. Learn how this 1969 algorithm catches almost every single-digit typo and most digit swaps — the same math you can verify yourself in our Aadhaar Format Validator.

16 May 2026

5 min read

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