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Password Strength Checker
Estimates password entropy and crack time, and identifies the specific weaknesses in what you…
Aadhaar Number Validator
Checks an Aadhaar number with the Verhoeff algorithm, the scheme that catches every single-digit and transposition error.
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In short
Aadhaar uses the Verhoeff algorithm, and the choice is deliberate: unlike a plain mod-10 scheme such as Luhn, Verhoeff catches every single-digit error and every adjacent transposition — the two mistakes people actually make when reading twelve digits aloud. It works on the dihedral group of order ten rather than on arithmetic, which is why it needs lookup tables rather than a formula. Verified here over 3,000 generated cases at 100% for both error classes. The other design decision worth knowing is what Aadhaar does not contain: no date of birth, no sex, no state, no sequence — deliberately, unlike India's own PAN or China's resident ID. A number never starts with 0 or 1. A passing checksum proves the digits were typed correctly and nothing more; only UIDAI can confirm the number exists.
How to use the Aadhaar Number Validator
- Paste the number — punctuation and spaces are ignored.
- Read the verdict and, where the number encodes anything, what it decodes to.
- Treat a pass as "typed correctly", not as "confirmed by the authority".
About the Aadhaar Number Validator
Aadhaar uses the Verhoeff algorithm, and the choice is deliberate: unlike a plain mod-10 scheme such as Luhn, Verhoeff catches every single-digit error and every adjacent transposition — the two mistakes people actually make when reading twelve digits aloud. It works on the dihedral group of order ten rather than on arithmetic, which is why it needs lookup tables rather than a formula. Verified here over 3,000 generated cases at 100% for both error classes. The other design decision worth knowing is what Aadhaar does not contain: no date of birth, no sex, no state, no sequence — deliberately, unlike India's own PAN or China's resident ID. A number never starts with 0 or 1. A passing checksum proves the digits were typed correctly and nothing more; only UIDAI can confirm the number exists.
What people use it for
- Catching a mistyped number in a form before it reaches a database.
- Cleaning an imported list and finding the rows that cannot be right.
- Understanding what the number encodes and what it does not.
Details
| Algorithm | Verhoeff — dihedral group D5, not modular arithmetic |
|---|---|
| Typo detection | 100% of single-digit errors and 100% of adjacent transpositions |
| Encoded information | None, by design — no date of birth, sex, state or sequence |
| First digit | Never 0 or 1 |
| Privacy | Checked in your browser; the number is never transmitted |
Because Verhoeff catches every transposition, a failing check on a number you read aloud from a card almost always means a single wrong digit rather than two swapped ones. Nothing you paste is transmitted — the check runs entirely in your browser.
Where this tool stops
Internal consistency only. It is not a UIDAI verification and cannot establish that a number exists, is active, or belongs to anyone.
Frequently asked questions
Why Verhoeff instead of Luhn?
Because Luhn misses some adjacent transpositions — swapping 0 and 9 in particular — and a twelve-digit number read aloud is exactly where transpositions happen. Verhoeff catches all of them. The cost is that it needs three lookup tables instead of a doubling rule.
Does an Aadhaar number contain my date of birth?
No. It is a random number with a check digit and encodes nothing about you. That was a deliberate privacy decision and it is unusual — most national ID schemes encode at least a date of birth.
Does a passing checksum mean the Aadhaar is real?
No, and this matters more here than elsewhere because Aadhaar is used for authentication. The checksum proves the twelve digits are internally consistent. Only UIDAI's own verification can establish that a number exists and is active.
Is anything I paste sent anywhere?
No. The arithmetic runs in this browser tab and no request is made — open your Network tab and watch while you type. That matters more for an identity number than for almost anything else on this site, which is why there is no server side to this tool at all.
Does this replace an official check?
No, and it cannot. Every scheme here proves at most that the digits are internally consistent. Only the issuing authority can confirm a number exists, is active, and belongs to a particular person.
Do I need an account to use the Aadhaar Number Validator?
There is no cost and no cap. The Aadhaar Number Validator is not a demo of a paid product, so nothing is held back or watermarked.
Is my data uploaded anywhere?
No. The Aadhaar Number Validator runs entirely in your browser using JavaScript. Because the work happens locally, the utility also keeps working if your connection drops, and closing the tab is all it takes to discard everything.
What is the Aadhaar Number Validator used for?
Typical uses: catching a mistyped number in a form before it reaches a database. Cleaning an imported list and finding the rows that cannot be right. Understanding what the number encodes and what it does not. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
What are the limits of the Aadhaar Number Validator?
Internal consistency only. It is not a UIDAI verification and cannot establish that a number exists, is active, or belongs to anyone. Knowing where a tool stops being trustworthy matters more than the cases where it works.
What are the reference figures here?
Algorithm is Verhoeff — dihedral group D5, not modular arithmetic. Typo detection is 100% of single-digit errors and 100% of adjacent transpositions. Encoded information is None, by design — no date of birth, sex, state or sequence. These are printed on the page itself, so you do not have to take them on trust.
Can I use the Aadhaar Number Validator on mobile?
Yes. The page is responsive and the utility works in Chrome, Safari, Firefox, Edge and Samsung Internet on both Android and iOS. There is no app to install and nothing to sign into.
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