identify_format

dev.toolstop/check-digits · Verify this server

Identify a bare number whose type was never recorded. Tests it against every supported format and reports which ones its check digit satisfies. Use it for an unlabeled spreadsheet column, a value pulled out of a log line or a scanned document, or any number handed over without being named. Reports every format that matches rather than choosing between them. Several matches is normal and does not mean the answer is unclear: some formats are subsets of others, so every ISBN-13 is also a valid EAN-13, and a short value can satisfy two unrelated formats by chance. Read one match as strong evidence and several as a set to narrow from context. As with validation, a match means the arithmetic is consistent, not that the identifier is registered or real.