IBAN validation guide for developers

Short summary

A practical guide to IBAN validation covering country-specific length checks and the mod-97 checksum algorithm with working JavaScript code. The key implementation detail is computing mod-97 in chunks since IBANs exceed JavaScript's Number precision. A passing checksum confirms format validity only—not that the account exists or belongs to the payer.

• •IBAN validation requires country-specific length check plus mod-97 checksum, not just regex
• •Chunked modulo loop needed because IBAN numbers exceed JS Number precision (2^53)
• •Valid checksum means well-formed IBAN, not that the account exists or is open

Generated with AI, which can make mistakes.