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About this tool
Mask Aadhaar numbers locally, validate 12-digit format, run checksum checks, and export privacy-safe masked lists.
The Aadhaar Masking Tool masks Aadhaar numbers and checks their structure locally: it strips formatting to 12 digits, runs the Verhoeff checksum that Aadhaar numbers are built on, and rewrites each number with only the digits you choose left visible. Four masking modes are available — full mask, last 2, last 4 (the convention UIDAI's own masked Aadhaar uses), or first and last 4 — with a mask character of your choosing. Paste a whole list separated by newlines, commas, semicolons, pipes or tabs and export the masked results as CSV; the numbers are processed in the page and never sent anywhere.
Open Aadhaar Masking Tool on AltFTool — it loads instantly in your browser.
Choose Single and type a number into 'Aadhaar number', or choose Bulk and paste a list one per line.
Pick a masking mode — Show last 4, Show last 2, Show first & last 4 or Full mask — and set the mask char.
Read the Formatted, Masked, Checksum and Privacy score cards, then press 'Copy Masked' or CSV to save aadhaar-masked-list.csv.
Every 12-digit entry is run through the Verhoeff dihedral-group checksum, so transposed or mistyped digits are caught, not just wrong-length input.
Full mask, last 2, last 4 or first-and-last-4, so you can match whatever the receiving form actually requires.
A pasted list is split on newlines, commas, semicolons, pipes or tabs, and exports with the masked value, format status, checksum result and the specific issue for each row.
The standard masked form leaves only the last four digits visible and hides the first eight, which is what UIDAI's own masked Aadhaar download produces. This tool defaults to that pattern and also offers last-2 and full masking when even four digits is more than the recipient needs.
Four things are flagged: fewer or more than 12 digits, any letters in the input, a first digit of 0 or 1 (Aadhaar numbers do not begin with either), and a failed Verhoeff checksum. All twelve digits being identical is flagged separately as an unrealistic pattern.
No. It only confirms the number is well-formed and its checksum is internally consistent. A number can pass every check here and still not be issued to anyone — real verification requires UIDAI's own authentication or offline eKYC channels, not arithmetic on the digits.
The numbers are read, masked and exported entirely in your browser — there is no upload, no server call and no storage. Even so, treat Aadhaar data as sensitive: close the tab when you are done, and remember that under Indian rules only masked or authorised forms of the number should be shared or retained by most organisations.
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