One column, three kinds of ID. GSTIN, PAN and Aadhaar in the same paste — check digit, state, holder type, duplicates marked, Aadhaar masked.
Paste one ID or four hundred — GSTIN check digit and state, PAN holder type, Aadhaar Verhoeff, duplicates marked, CSV back. Nothing leaves your browser.
Classifies every pasted line by shape and checks it. GSTIN: the GSTN mod-36 check character (weights alternating 2/1 from the right), the state code against the full `01`–`38` + `97`/`99` list with `25` and `28` flagged as retired rather than failed, the PAN slot decoded to a holder type — or reported as a TAN or a non-PAN-based non-resident/UIN registration, never failed for it — the 13th character (never `0`) and the 14th (`Z` regular, `D` TDS deductor, `C` TCS collector, a.