Find the original number
Read the digits printed below the product’s barcode or request the identifier from the brand owner or supplier. If you only have a marketplace listing, confirm that it is the exact product and variant rather than assuming a nearby listing is correct.
A store’s internal SKU is not automatically an EAN. Keep any leading zeroes and avoid spreadsheet number formatting that can change the original string.
Check length and checksum
Choose the format you actually have: EAN-13 contains 13 digits, EAN-8 eight and UPC-A twelve. A check digit calculation uses the preceding data digits to detect some errors.
For example, 4006381333931 has a correct EAN-13 checksum; changing its last digit to 2 makes it fail. This is an arithmetic illustration, not an identifier offered for use on your products.
Check identity separately
Verified by GS1 provides identity information associated with GS1 keys. Use it, together with assignment records and the sales channel’s requirements, when the question is who or what the number represents.
A correct checksum is not evidence of ownership, a licence or retailer acceptance. A check digit cannot tell whether the product description on a label is truthful.
If your starting point is a barcode photo
AIQRGO’s current image reader decodes QR codes only. It is not an online UPC or EAN image scanner. Read the human-readable digits from a clear image, or use a scanner supporting the relevant linear format, then validate the decoded number.
If the digits are unclear, ask for the source record or a sharper image instead of guessing. A decoder and a product lookup service solve different problems.