Validate ISBN-10 and ISBN-13 book identifiers with check digit verification. Auto-detects format and converts ISBN-10 to ISBN-13.
Hyphens and spaces are ignored. Supports ISBN-10 and ISBN-13.
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An International Standard Book Number (ISBN) is a unique numeric identifier assigned to books and book-like products. It helps publishers, libraries, booksellers, and readers reliably identify and order specific editions of a book.
ISBN-10: Multiply each of the first 9 digits by its position weight (10, 9, 8, ..., 2), sum them, then compute (11 - sum mod 11) mod 11. If the result is 10, the check digit is X.
ISBN-13: Multiply each of the first 12 digits alternately by 1 and 3, sum them, then compute (10 - sum mod 10) mod 10.
Prepend "978" to the first 9 digits of the ISBN-10 (dropping the old check digit), then recalculate the check digit using the ISBN-13 algorithm.