ISSN validator
Check that an ISSN is well formed and that its check digit is correct.
Your data does not go to our server. This tool runs in your browser; what you type or open never leaves your device.
This tool needs JavaScript, because it runs only in your browser. Turn JavaScript on to use it. How it works: the first seven digits are multiplied by 8 down to 2, the sum is divided by 11, and the check digit is 11 minus the remainder (X means 10).
Questions
What does a valid check digit prove?
Only that the number has no typing error. It does not prove that the ISSN was assigned to a journal; the ISSN Portal answers that.
Why is the last character sometimes X?
X stands for the check value 10.