What an IBAN is

Swift's page says the IBAN is an international standard for identifying account numbers, to support automated cross-border payments, and that each country has its own national format specified under ISO 13616. ISO designated Swift as the registration authority for national IBAN formats, and only a national standards body or a national central bank can request registration of a format. Swift publishes the ISO 13616 IBAN Registry as a free PDF and TXT download (Swift).

What the checker tests

Letters and digits only, with a two-letter country code and two check digits at the start.
A length between 15 and 34 characters.
The check digits, using the standard modulo 97 test. The Swift page we read does not describe this test; it comes from general knowledge of the standard.

What it does not test

Country-specific length and format. Each country's format is in the registry, which we did not load into the tool.
That the account exists, is open or belongs to the person you mean.
Name match. In the euro area a name check may be offered by your bank; see verification of payee.

How to read the result

A pass means a typing error is unlikely. A fail usually means a mistyped or missing character; confirm the IBAN with the recipient. A pass does not protect you from a fraudster's valid IBAN.

The example

The pre-filled IBAN is a widely published example, not a real account. Replace it with yours; nothing leaves your browser.

Use the BIC checker for the bank identifier.