The 12-digit Aadhaar number
Every Aadhaar number is a 12-digit number issued by the Unique Identification Authority of India (UIDAI). On the card and in most documents it is printed as three groups of four digits. Using one of UIDAI's published sandbox numbers as an example:
| Position | Rule | Why |
|---|---|---|
| Digit 1 | 2 – 9, never 0 or 1 | Reserved by UIDAI's numbering scheme; also avoids leading-zero problems in software. |
| Digits 2 – 11 | Random | Deliberately meaningless so the number reveals nothing about the holder. |
| Digit 12 | Verhoeff check digit | Catches every single-digit typo and every adjacent swap. See the Verhoeff guide. |
No hidden meaning
Unlike a PAN (which encodes the holder type) or a GSTIN (which encodes the state), an Aadhaar number is intentionally random. It does not contain your state, district, date of birth, gender or enrolment date. Two family members enrolled on the same day at the same centre get unrelated numbers. Anyone claiming to "decode" an Aadhaar number is guessing.
Spaces and formatting
The spaces are purely for readability. Systems should strip them before storing or validating, and the canonical regex for the digits themselves is ^[2-9][0-9]{11}$. The developer page has versions that accept the spaced form.
Masked Aadhaar (XXXX XXXX 7058)
A masked Aadhaar hides the first eight digits and shows only the last four. UIDAI offers a Masked Aadhaar download option on the myAadhaar portal, and this is the version you should share when an organisation only needs to see that you hold an Aadhaar — hotels, event check-ins, and most private verifications. The last four digits are enough to match against a number an authorised party already holds, but not enough to reconstruct it.
Software that displays Aadhaar numbers should follow the same convention. It is also what UIDAI's own Aadhaar-related regulations expect of entities storing the number.
Aadhaar Virtual ID (16 digits)
A Virtual ID (VID) is a temporary 16-digit number mapped to your Aadhaar number that you can use for authentication instead of the Aadhaar number itself. It follows the same conventions: first digit 2 – 9, random middle, Verhoeff check digit at the end. You can generate a new one at any time, which invalidates the old one. Details and a validator are on the VID page.
Enrolment ID (28 characters)
After enrolment or an update you receive an acknowledgement slip with an Enrolment ID (EID). It is not an Aadhaar number and cannot be used for authentication. It has two parts:
- a 14-digit enrolment number, printed as
1234/12345/12345, and - the date and time of enrolment, 14 digits in
dd/mm/yyyy hh:mm:ssform.
Together they are entered as 28 digits (without separators) on the myAadhaar portal to check enrolment status or retrieve a lost Aadhaar number.
Comparison of Aadhaar-related identifiers
| Identifier | Length | Permanent? | Checksum | Used for |
|---|---|---|---|---|
| Aadhaar number (UID) | 12 digits | Yes | Verhoeff | Identity, authentication, e-KYC |
| Virtual ID (VID) | 16 digits | No, replaceable | Verhoeff | Authentication without revealing UID |
| Masked Aadhaar | 4 visible digits | — | — | Sharing proof of Aadhaar with minimal exposure |
| Enrolment ID (EID) | 28 digits | Per enrolment/update | None | Tracking an application |
Common mistakes when handling the format
- Spreadsheets dropping digits. Excel turns 999941057058 into 9.99941E+11 unless the cell is text.
- Accepting 0 or 1 as the first digit. A regex like
\d{12}lets through numbers that cannot exist. - Skipping the checksum. About 10% of random 12-digit strings pass a length-only check; almost none pass Verhoeff.
- Confusing EID with UID. A 14- or 28-digit number from an enrolment slip is not an Aadhaar number.
Frequently asked questions
How many digits are in an Aadhaar number?
Exactly 12. It is normally printed as three groups of four digits, for example 9999 4105 7058.
Can an Aadhaar number start with 0 or 1?
No. UIDAI's numbering scheme never issues numbers whose first digit is 0 or 1, so every genuine Aadhaar number starts with 2 through 9.
Does the Aadhaar number encode my state, birth date or gender?
No. The first 11 digits are random and carry no personal information. Only the 12th digit has structure: it is a Verhoeff check digit computed from the other 11.
What is a masked Aadhaar number?
A masked Aadhaar shows only the last four digits, with the first eight replaced by X (XXXX XXXX 7058). UIDAI lets you download a masked Aadhaar from myAadhaar, and it is the recommended form to share when the full number is not required.
What is the difference between Aadhaar number, VID and enrolment ID?
The Aadhaar number is the permanent 12-digit ID. A Virtual ID is a temporary 16-digit stand-in for it. The enrolment ID (EID) is the 28-character reference on your enrolment slip: a 14-digit enrolment number followed by the 14-digit date and time of enrolment, used only to track the application.