Why an Indian ID format validator exists
Every Indian developer has re-googled the same regexes a dozen times: the PAN pattern, the IFSC structure, the mobile-number rule. And every Indian filling a form has faced the small panic of a rejected field: was that a zero or the letter O? A format validator answers that in one second - before you submit, before a transfer fails, before a KYC form bounces.
Most online checkers stop at a regex. A regex catches typos in shape, but a made-up number sails through it. This page goes one level deeper: real checksum logic - the Verhoeff check digit UIDAI builds into every Aadhaar number, and the mod-36 check digit built into every GSTIN. A random or fabricated number has roughly a 1-in-10 (Aadhaar) or 1-in-36 (GSTIN) chance of surviving the checksum, so a pass here means something a regex alone cannot say.
How to validate an IFSC code
An IFSC (Indian Financial System Code) is 11 characters with a rigid anatomy: the first 4 letters are the bank code (SBIN for State Bank of India, HDFC for HDFC Bank), the 5th character is always 0, and the last 6 characters identify the branch. Paste the code above and the tool checks each part - then decodes the bank name from the bank code using a public bank-code dataset.
What this check does not do: prove the branch exists. The structure can be perfect while pointing at a branch code the bank never issued. For an actual transfer, cross-check the code against the bank's own branch directory or your passbook. The validator's job is catching the typo before you send money to the wrong place.
PAN card number format, decoded
A PAN is 10 characters: 5 letters, 4 digits, 1 letter (AAAAA9999A). But the format carries meaning most people never notice. The 4th character encodes the holder type: P for Individual, C for Company, H for Hindu Undivided Family (HUF), F for Firm or Partnership, A for Association of Persons (AOP), T for Trust, B for Body of Individuals (BOI), L for Local Authority, J for Artificial Judicial Person, and G for Government. The tool decodes this for you - a PAN whose 4th character is not one of these is structurally invalid, something a plain regex often misses.
The most common PAN format errors are boring ones: lowercase entry, confusing 0 (zero) with O (letter O), and stray spaces. The validator normalises all three before checking, so a rejection here means the number itself is malformed.
Aadhaar validation: the Verhoeff checksum
An Aadhaar number is 12 digits, never starts with 0 or 1, and - this is the interesting part - its 12th digit is a check digit computed with the Verhoeff algorithm. UIDAI chose Verhoeff deliberately: unlike a simple digit sum, it catches every single-digit typo and every swap of two neighbouring digits (typing 32 instead of 23), which are the two most common human entry errors.
One firm boundary: a checksum pass proves the number is well-formed, not that it was issued or belongs to anyone. Real Aadhaar verification is legally restricted to UIDAI-authorized entities under the Aadhaar Act, 2016. No website can do that check for you - and any site claiming to is either lying or breaking the law.
How the GSTIN checksum works
A GSTIN is 15 characters with a beautiful nested structure: a 2-digit state code (27 = Maharashtra, 29 = Karnataka), a 10-character PAN embedded inside it, an entity code, the letter Z, and a final check digit. The check digit uses a mod-36 algorithm from the ISO 7064 family: each of the first 14 characters maps to a 36-symbol alphabet (0-9 then A-Z), weighted alternately by 1 and 2, and the 15th character must match the computed value.
The validator decodes all of it - state name, embedded PAN (re-validated as a PAN), entity number, check digit - so a single typo anywhere in the 15 characters gets caught, and you can see exactly which part failed.
Format check vs real verification - read this
This distinction matters, so here it is plainly. Format validation (what this page does) proves a number could have been issued: right shape, right checksum. Verification proves a number was issued and belongs to someone - and that lives only with the issuing authority.
The official paths: the Income Tax e-filing portal has a Verify Your PAN service; the GST portal has a public taxpayer search that shows whether a GSTIN is registered and active; Aadhaar verification requires UIDAI-authorized services. Use this page as the quick pre-submission typo-catcher, and the official portals as the proof.
Common uses
Before submitting KYC forms. Catch the typo in your PAN or Aadhaar before the portal rejects it - or worse, before a silent mismatch blocks you later.
Before a bank transfer. Validate the beneficiary's IFSC structure before initiating NEFT, RTGS or IMPS - a wrong 5th character is caught here in a second.
Vendor GSTIN sanity checks. A supplier's GSTIN that fails the checksum is either mistyped or fabricated. Either way, you want to know before the invoice.
Developer form validation. Testing the exact rules your signup form will enforce - see precisely which rule rejects an input, with a human-readable reason.