ISIN Validator (Securities Identifier Check)

It checks the structure and checksum: that the code is 12 characters made of a two-letter country prefix, a nine-character alphanumeric NSIN, and a final numeric check digit, and that the check digit matches the Luhn calculation. A valid result means the code is well-formed, not that a security with that ISIN is currently listed.

First every letter in the first 11 characters is expanded to a two-digit number, where A is 10, B is 11, up to Z which is 35. Digits stay as they are. The resulting all-digit string is run through the Luhn algorithm, and the check digit is the value that makes the total a multiple of 10.

An ISIN is a global 12-character identifier that usually embeds a national identifier inside it. For US and Canadian securities that inner part is the 9-character CUSIP, and for UK securities it is the 7-character SEDOL. The ISIN adds a country prefix and its own check digit on top of the national code.

The most common cause is a single mistyped character, which breaks the Luhn checksum. Other causes are the wrong length, a missing country prefix, or a non-numeric final character. The validator shows the computed check digit so you can compare it with the one you entered.

No. All validation runs locally in your browser using client-side JavaScript. The ISIN you enter is never uploaded, logged, or stored, so it never leaves your device.