Canadian · Validation
ISNI number validator & check character calculator.
Check a 16-character International Standard Name Identifier (ISO 27729), or enter just the first 15 digits to have the correct final character computed. This checks format and checksum only. Everything runs in your browser: nothing you type is transmitted anywhere.
Inputs
Result
Enter an ISNI and press Validate.
How the ISNI check character works
An ISNI is 16 characters, normally shown as four groups of four separated by spaces. The first 15 are digits and the last is a check character, calculated with ISO/IEC 7064 MOD 11-2. Start with a total of 0; for each of the 15 digits, add the digit to the total and double the result. Take the total modulo 11, subtract it from 12, and take that modulo 11 again. A result of 10 is written as the letter X. This is the algorithm python-stdnum implements (stdnum/isni.py with stdnum/iso7064/mod_11_2.py), and it agrees with the description on Wikipedia.
The python-stdnum example ISNI 0000 0001 2281 955X and Wikipedia's example 0000 0001 2146 438X both end in X, which is what the algorithm gives for their first 15 digits. ORCID iDs use the same algorithm and are drawn from a block reserved within the ISNI number space, so ORCID iDs are a subset: every valid ORCID iD also passes here, but the ORCID validator is the better fit for researcher IDs.
What a passing checksum does and doesn’t tell you
A valid check character only proves the 16 characters are internally consistent. It does not confirm the ISNI was ever assigned or who it belongs to; look it up at isni.org for that. This tool checks format and checksum only, runs entirely in your browser, and nothing you type is transmitted, stored, or logged.