ISBN Validator

How to use

1. 1Pick Single ISBN to validate one number, or Batch list to paste many ISBNs at once.
2. 2Type or paste an ISBN-10 or ISBN-13. Dashes, spaces, and lowercase x are normalized for you.
3. 3Read the verdict, the detected kind (ISBN-10 or ISBN-13), and the expected check character when the input fails.
4. 4Use the Conversion panel to copy the equivalent ISBN-13 (from a valid ISBN-10) or the equivalent ISBN-10 (from an ISBN-13 starting with 978).
5. 5Pick a display format: compact, spaced, or dashed. Click Copy to send the chosen form to your clipboard.

About this tool

ISBN Validator checks whether an ISBN-10 or ISBN-13 number is well-formed, computes the expected check character when the input has a typo, and converts between the two formats when conversion is defined. ISBN-10 is verified with the ISO 2108 mod-11 weighted sum: each of the ten characters is weighted from 10 down to 1, positions one through nine must be digits, and the final character may be a digit or the letter X (which stands for the value 10); a valid ISBN-10 has a weighted sum that is a multiple of 11. ISBN-13 uses the EAN-13 algorithm: digits in odd positions keep their value, digits in even positions are multiplied by 3, and a valid ISBN-13 has a weighted sum that is a multiple of 10. The tool also confirms that ISBN-13 values start with one of the two bookland prefixes (978 or 979). Conversion is straightforward in one direction and bounded in the other: every valid ISBN-10 maps to a unique ISBN-13 by prepending 978 and recomputing the EAN-13 check digit, and every ISBN-13 that starts with 978 can be mapped back by dropping the prefix, keeping the next nine digits, and recomputing the ISBN-10 check character; ISBN-13 values that start with 979 have no ISBN-10 equivalent because the 979 range was allocated after the ISBN-10 space was full and the spec does not define a mapping back. Three display formats are provided: compact (no separators), spaced (EAN-13 style groups), and dashed (a structurally valid group layout with the check character on its own). The dashed layout is labelled as display-only because registrant-accurate hyphenation requires the live International ISBN Agency ranges file, which changes when new ranges are allocated. A batch mode validates one ISBN per line and reports the count of valid and invalid rows, the detected kind, and the converted equivalent for each row, plus copy buttons for the valid ISBNs and the converted ISBN-13 list. Useful for librarians, booksellers, publishers, authors, library cataloguers, indie bookstore owners, academic researchers, bibliographic database editors, and anyone who needs to confirm an ISBN is well-formed before saving it to a record. Everything runs locally in JavaScript, so the ISBNs you paste here are never uploaded to a server.

Free to use. Works in your browser. No signup, no login.