Validate an ISBN-10 or ISBN-13 book number with its checksum online, in your browser.
Validate a book's ISBN. The tool detects whether it is ISBN-10 or ISBN-13 and verifies the check digit, ignoring hyphens and spaces.
ISBN-13 (starting 978/979) is the current standard; ISBN-10 is the older form. Each uses a different checksum, both supported here.
Usually a mistyped digit or a wrong check digit. The last character (which can be X for ISBN-10) must match the computed checksum.