A clear look under the hood
How we validate
an IBAN.
IBANChopper checks the parts of an IBAN that can be verified from the number itself. Everything happens locally in your browser.
Normalization
We trim leading and trailing whitespace, remove spaces between characters, and uppercase letters. We don’t silently remove arbitrary punctuation or alter characters that could hide a typo.
Country rules
We identify the country from its two-letter prefix and compare the number with that country’s official length and BBAN structure. Country rules are kept as data, not buried in interface code.
MOD-97
We move the country code and check digits to the end, convert letters to numbers, and calculate the remainder incrementally. A remainder of 1 passes the international checksum.
What “valid” means
A structurally valid IBAN has the expected format and checksum. It does not prove that an account currently exists, accepts payments, or belongs to a particular person or organization.