Aadhaar Card Validator
Online Indian Aadhaar Card validator. Verify format and Verhoeff check digit.
How does Aadhaar Card validation work?
Validation checks if the number has exactly 12 digits, if the first character is not '0' or '1', and executes the complex geometric check of the Verhoeff algorithm.
The Verhoeff algorithm uses dihedral group D5 multiplication tables, positional permutations, and inverses to verify if the final checksum is zero. This logic is highly robust at detecting transposition errors.
Anatomy & Structure of the Aadhaar Card (आधार)
Aadhaar is a 12-digit unique identity number issued by UIDAI structured in 3 parts:
| Position | Field | Length | Meaning & Rule | Example |
|---|---|---|---|---|
| 1 | Leading Digit | 1 digit | Official constraint: cannot be 0 or 1 (valid range: 2 to 9) | 2 |
| 2 to 11 | Random Number | 10 digits | Randomized identifier with no embedded personal data | 3456789012 |
| 12 | Check Digit | 1 digit | Calculated strictly via Verhoeff checksum algorithm (dihedral group D5) | 3 |
Official Algorithm (Verhoeff Checksum — UIDAI)
Aadhaar uses the Verhoeff algorithm based on the dihedral group D5:
c = inv(Σ_perm(d[i], pos[i]))
- 1. Reverse the string and process digits from right to left.
- 2. Apply permutation matrix P to each digit based on its position index.
- 3. Cumulatively multiply values using the D5 dihedral group multiplication table.
- 4. The check digit is the inverse table lookup that brings total checksum to 0.
- 5. Detects 100% of single-digit errors and adjacent transposition errors.