What does a passing checksum actually confirm?

It confirms the IBAN is internally consistent — the check digits in positions 3 and 4 correctly match the rest of the number under the MOD-97 algorithm defined by ISO 13616. That catches typos, transposed digits, and made-up numbers. It does not confirm the account exists, belongs to anyone, or can currently receive a payment — that requires checking with the account-holding bank.

Why does it check length separately from the checksum?

Each IBAN country has a fixed total length — Germany is always 22 characters, the UK is always 22, France is always 27, and so on. A wrong length is a different problem from a wrong checksum: it usually means digits were dropped or extra characters were typed, and it's worth surfacing on its own rather than lumping it into a generic "invalid" result.

What if the country code isn't recognized?

You'll see "unknown country code" instead of a pass/fail. This tool's length table covers the roughly 60 countries that currently issue IBANs. If a country isn't on that list, there's no way to check its expected length here — you'd need to confirm it against your bank's documentation, since the checksum math alone can't validate a scheme this tool doesn't know the rules for.

Is my IBAN uploaded or saved anywhere?

No. The checksum calculation, length check, and formatting all run locally in your browser using plain JavaScript. The IBAN never leaves your device — it isn't sent to a server, written to a log, or included in any analytics event.

IBAN VALIDATOR

Check the MOD-97 checksum and country length rules. The IBAN is never transmitted, logged, or stored — it stays on your device, full stop.

This IBAN is checked entirely on your device. It is never sent to a server, logged, or stored — not even in analytics.

IBAN

Valid IBAN

Checksum and length both check out.

Formatted	GB29 NWBK 6016 1331 9268 19
Country	United Kingdom (GB)
Length	22 (expected 22)
MOD-97 checksum	Pass

How to validate an IBAN

1
Type or paste an IBAN, with or without spaces.
2
See it grouped into the standard 4-character blocks, with the country it belongs to.
3
Check whether the length matches that country's fixed IBAN length and whether the MOD-97 checksum passes.

Questions

What does a passing checksum actually confirm?: It confirms the IBAN is internally consistent — the check digits in positions 3 and 4 correctly match the rest of the number under the MOD-97 algorithm defined by ISO 13616. That catches typos, transposed digits, and made-up numbers. It does not confirm the account exists, belongs to anyone, or can currently receive a payment — that requires checking with the account-holding bank.
Why does it check length separately from the checksum?: Each IBAN country has a fixed total length — Germany is always 22 characters, the UK is always 22, France is always 27, and so on. A wrong length is a different problem from a wrong checksum: it usually means digits were dropped or extra characters were typed, and it's worth surfacing on its own rather than lumping it into a generic "invalid" result.
What if the country code isn't recognized?: You'll see "unknown country code" instead of a pass/fail. This tool's length table covers the roughly 60 countries that currently issue IBANs. If a country isn't on that list, there's no way to check its expected length here — you'd need to confirm it against your bank's documentation, since the checksum math alone can't validate a scheme this tool doesn't know the rules for.
Is my IBAN uploaded or saved anywhere?: No. The checksum calculation, length check, and formatting all run locally in your browser using plain JavaScript. The IBAN never leaves your device — it isn't sent to a server, written to a log, or included in any analytics event.