According to the ISBN specification, a certain prefix has been assigned to ISBN numbers. I have added a check for this, since it would pass validation for valid GTIN numbers that are not actually ISBN numbers.
For a 13-digit ISBN, a prefix element – a GS1 prefix: so far 978 or 979 have been made available by GS1.
olivervogel
commented
9 months ago
According to the ISBN specification, a certain prefix has been assigned to ISBN numbers. I have added a check for this, since it would pass validation for valid GTIN numbers that are not actually ISBN numbers.
For a 13-digit ISBN, a prefix element – a GS1 prefix: so far 978 or 979 have been made available by GS1.