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ISNI Validator

Enter an ISNI to verify its check digit.

How it is calculated

Paste an ISNI with or without spaces and hyphens; both are removed first, and letters are read in uppercase, so a lowercase x works. What remains must be exactly 16 characters: 15 digits followed by a digit or X. Anything else (wrong length, letters among the first 15, a final character other than 0-9 or X) gives no result. The check character is computed over the first 15 digits: start with a total of 0 and, for each digit, set total = (total + digit) × 2. Then remainder = total mod 11 and check = (12 − remainder) mod 11, written as X when the value is 10. If this equals the last character you typed, the result is Valid. The tool also echoes the number in groups of four. It checks only the arithmetic, so it cannot tell whether the ISNI is actually assigned to someone.

Worked example

Check 0000 0001 2281 955X. The 15 digits are 000000012281955. Running the formula from the left, the zeros keep the total at 0; then the digit 1 gives (0 + 1) × 2 = 2; digit 2 gives 8; digit 2 gives 20; digit 8 gives 56; digit 1 gives 114; digit 9 gives 246; digit 5 gives 502; and the last digit 5 gives 1014. Now 1014 mod 11 = 2 and (12 − 2) mod 11 = 10, which is written X. That matches the final character, so the tool echoes 0000 0001 2281 955X as Valid. Changing the last character to 1 would make it Invalid.

Try this example →

Common mistakes

  • Treating Valid as proof the identifier exists. A correct check character only means the number is internally consistent; it can still be unassigned or belong to someone other than you expect.
  • Entering the 16-digit ISNI with an ORCID or ISBN-style prefix, or a URL such as https://isni.org/isni/.... Only the 16 characters are accepted, so remove everything else first.
  • Typing a lowercase or look-alike X (such as a multiplication sign or the Cyrillic letter). Lowercase x is accepted, but other characters give no result.
  • Dropping a leading zero. ISNIs often start with several zeros, and a 15-character string without one gives no result, not Invalid.
  • Expecting the tool to correct the number. It shows the check character that should end the 15 digits, but whether a digit in the first 15 positions is the typo is for you to find.

About this calculator

The ISNI (International Standard Name Identifier) is a 16-digit identifier — formatted as four groups of four characters — assigned to public identities such as authors, performers, researchers and organizations, so the same person or entity can be recognized consistently across libraries, publishing databases and rights-management systems, much like an ISBN identifies a book.

The final character of an ISNI is a check digit computed with the ISO 7064 MOD 11-2 algorithm over the preceding 15 digits, letting any system detect a mistyped or corrupted ISNI without needing to look it up in a database. This calculator recomputes that check digit from the ISNI you enter and confirms whether it matches, showing the expected check character.

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  • Editorial team

    An ORCID iD is a special range of ISNI and uses the very same check character, so you can paste a bare ORCID such as 0000-0002-1825-0097 here and see Valid. Remove any web address in front of it first. Remember that a matching check character only shows the typing is consistent, not who owns the number. Do you check identifiers one at a time, or would a list of them be more useful to you?

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