UPC-A check digit validator
Prefix a 0 to make 13 digits, then apply the same alternating 1/3 weighting as EAN-13.
036000291452 is a valid UPC-A: the check digit match.
A passing checksum only proves the number is arithmetically self-consistent. It does not prove an IBAN names an open account, an ISBN is assigned to a real book, or a card is active, unstolen, or has funds. Those require asking the bank, the ISBN registry, or the card network.
Try it: a valid example · a broken example
curl 'https://check-digit.gumballtools.com/api/v1/run?input=036000291452&format=upca'