ISBN validator
Check an ISBN-10 or ISBN-13 and inspect its check digit.
- ISBN check digits
- ISBN conversion
Checksum tests
ISBN-13 / EAN-13Check digit validmod 10 with alternating weights 1 and 3
Luhn (cards, IMEI)Check digit does not matchmod 10 with every second digit doubled
What this does not tell you
ExistenceNot checkedno network lookup is made, ever
Ownership or validity in useNot checked