ISBN Validator
Paste an ISBN-10 or ISBN-13 to check whether its check digit is correct.
Computed locally in your browser with the ISBN-10 (mod 11) and ISBN-13 (mod 10) check-digit schemes. Your ISBN stays only on this page.
Validate an ISBN check digit
Paste an ISBN-10 or ISBN-13 to confirm its check digit, see which scheme it matched, and read off the corrected value when the digit is wrong. ISBN-10 uses the mod-11 weights (where a trailing X means 10); ISBN-13 uses the alternating 1, 3 mod-10 scheme. Spaces and hyphens are ignored, so grouped input works as-is. Need to create valid fixtures instead? Try the ISBN-13 or ISBN-10 generators.