100% Client-Side · Zero PII Storage

Free Aadhaar Verhoeff Checksum & Format Validator

Validate Indian 12-digit Aadhaar number syntax, non-leading 0/1 rule, and mathematical Verhoeff Dihedral (D5) check digit in real time. Zero server calls, zero data retention.

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Sample test numbers:

Understanding the 12-Digit Aadhaar Structure

Under the Aadhaar (Targeted Delivery of Financial and Other Subsidies, Benefits and Services) Act, 2016, an Aadhaar number is a unique 12-digit random identification number containing no PII or demographic intelligence:

Key UIDAI Architectural Rules

  • Prefix Restriction: Valid Aadhaar numbers never begin with 0 or 1. The first digit must be within the range 2 to 9.
  • Dihedral Group D5 Checksum: The 12th digit is calculated using the Verhoeff algorithm. It detects 100% of single-digit transcription errors and 95.3% of transposed adjacent digits.
  • Mandatory 8-Digit Masking: Under Section 16 of the RBI Master Direction on KYC (2016, updated 2024), storing raw unmasked 12-digit Aadhaar numbers is illegal for non-banking entities. Storage must redact the first 8 digits (XXXXXXXX1234).

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Frequently Asked Questions

How does the Verhoeff checksum algorithm work on an Aadhaar number?

The Verhoeff algorithm is a checksum formula for error detection developed by Dutch mathematician Jacobus Verhoeff. It is based on the dihedral group D5 of order 10. By operating non-commutatively over non-symmetric multiplication and permutation tables, it reliably detects keystroke swaps (e.g. typing 43 instead of 34) that standard modulo-10 algorithms miss.

Does this tool store, log, or send my Aadhaar number over the internet?

No. This tool runs 100% in your local web browser using client-side JavaScript. No network requests are made, no packets leave your device, and zero data is written to any server or cookie.

Why do Aadhaar numbers never start with 0 or 1?

UIDAI reserved the initial digit ranges 0 and 1 for future administrative purposes and special numbering schemes. Standard citizen Aadhaar numbers always begin with digits 2 through 9.

How can fintechs verify active Aadhaar status legally without an Aadhaar Vault?

Regulated digital lenders and fintechs integrate the ASP Associates Aadhaar Verification API, which handles ephemeral in-memory processing. Payloads are verified against UIDAI KUA nodes and immediately returned with 8-digit masking, eliminating the requirement to maintain expensive certified Aadhaar Vaults.