ChemDataDoctor, the Spreadsheet Medic for CAS Numbers

Field notes

The tool accepts XLSX, XLS, CSV, TSV, or pasted cells and processes them in the browser. Its checks cover CAS number structure and check digits, spacing and dash normalization, duplicates, and spreadsheet date conversion; exports retain the original columns while adding cleaned values and notes. The page specifies limits of 50,000 rows, 200 columns, and 2 million workbook cells. It also says the source file is never changed and that processing occurs on the user's device.