IBAN Validator

Validate an IBAN's format and mod-97 checksum. Free, runs entirely in your browser — no signup, and nothing you paste in is uploaded.

An IBAN check is unusually satisfying because it is real arithmetic rather than a format guess. Move the first four characters to the end, replace every letter with a two-digit number based on its position in the alphabet, and the resulting integer must leave a remainder of one when divided by 97. That catches essentially every single-character typo.

Length is checked separately and is country-specific — Norway uses 15 characters, Malta 31 — so the country code determines what a valid length even is. And as with any checksum, arithmetic is all it proves: a structurally perfect IBAN can belong to no account whatsoever.