IBAN Validator

Validate IBAN account numbers via the standard mod-97 checksum. Decode country, bank code, branch code, account number from a single paste. Catch typos before they cost a wire transfer fee. All validation runs locally — your IBAN never reaches a server.

What an IBAN encodes

International Bank Account Number — a single string identifying a bank account anywhere in the IBAN-using world. Format:

DE 89  3704 0044  0532 0130 00
│  │   │             │
│  │   bank code     account number
│  check digits
country code

The check digits make the whole string self-validating via mod-97 — a wrong character almost certainly fails the checksum.

What this tool does

1. Strip whitespace.
2. Validate length matches the country’s IBAN format (each country has a fixed length).
3. Compute mod-97 over the rearranged numeric form.
4. Decode country, bank code, branch code, account number using the country’s specific layout.

If valid, you get a clean breakdown. If invalid, the tool tells you why — checksum failed, length wrong, country not recognized.

IBAN length by country

Each country fixes its IBAN length; a mismatch is an instant fail even before mod-97:

The tool carries the full ISO 13616 registry, so bank-specific checks (HSBC, Nordea, Askari, HBL, Bank Alfalah, Bank of Valletta) reduce to “does this string match the country’s format and checksum” — the issuing bank does not change the validation rule.

Validating an IBAN in code

The mod-97 check is short enough to inline:

$iban = strtoupper(preg_replace('/\s+/', '', $iban));
$rearranged = substr($iban, 4) . substr($iban, 0, 4);
$numeric = preg_replace_callback('/[A-Z]/', fn($m) => ord($m[0]) - 55, $rearranged);
$valid = bcmod($numeric, '97') === '1';                    // PHP

const s = iban.replace(/\s+/g, "").toUpperCase();
const r = (s.slice(4) + s.slice(0, 4)).replace(/[A-Z]/g, c => c.charCodeAt(0) - 55);
let rem = 0; for (const d of r) rem = (rem * 10 + +d) % 97;
const valid = rem === 1;                                    // JavaScript, overflow-safe

For Angular, wrap that in a Validator; for production, ibantools also checks per-country length and structure. This tool does all of it locally — paste to verify before you ship the regex.

Common workflows

Sanity-check before a wire transfer. Customer or coworker dictates an IBAN. Paste here. If invalid, ask for the correct number before initiating the transfer (and incurring the failed-wire fee).

Validate a payments form. Build server-side validation, but adding this tool to a docs page lets users debug their own input before submission.

Audit a stored set of IBANs. Run a list through to catch any that drifted (manual data entry, OCR errors).

Look up a bank. The bank code maps to a directory entry — your bank’s compliance team will use the country code + bank code to identify the institution.

Why local IBAN checking

IBANs are PII when paired with a name. Pasting them into a remote validation service exposes that pairing to whoever runs the site. Ours validates locally — paste freely, leave nothing behind.

Last updated: 2026-07-04