#isbn

ISBN validation and conversion as an API, computed locally and deterministically. The validate endpoint detects whether a code is an ISBN-10 or an ISBN-13, ignores hyphens and spaces, and verifies the check digit — ISBN-10 with the mod-11 scheme whose last character may be the letter X (for 10), and ISBN-13 with the weighted 1-3-1-3 mod-10 scheme — so 0-306-40615-2 and 978-0-306-40615-7 both validate while a wrong check digit is rejected. The checkdigit endpoint computes the trailing check digit for a 9-digit ISBN-10 stem or a 12-digit ISBN-13 stem (and recomputes it for a full code). The convert endpoint converts between the two forms: an ISBN-10 becomes an ISBN-13 by prefixing 978 and recomputing the check, and a 978-prefixed ISBN-13 converts back to ISBN-10 (979-prefixed codes have no ISBN-10 equivalent). Everything is computed locally and deterministically, so it is instant and private. Ideal for publishing, library, bookstore, catalogue, e-commerce and metadata app developers, ISBN-validation and barcode tools, and inventory systems. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is ISBN-specific validation and conversion; for generic Luhn/Verhoeff check digits use a check-digit API.

api.oanor.com/isbn-api

Validate and work with product and publication codes. Check the check digit of any EAN-8, UPC-A, EAN-13, GTIN-14, ISBN-10, ISBN-13 or ISSN code — the type is detected automatically and you get back whether it is valid plus the expected check digit. Compute the missing check digit for a partial code, and validate or convert ISBNs between the 10- and 13-digit forms. Hyphens and spaces are ignored, so you can paste codes straight from a label or catalogue. Pure local computation — no key, no third-party service, instant. Live. 4 endpoints. Built for retail and inventory systems, e-commerce catalogues, publishing, library tooling and data validation. Distinct from barcode image generation, payment-card (Luhn) and IBAN checks.

api.oanor.com/barcodecheck-api

Search millions of books, look up editions by ISBN-10/13 and find authors — with covers, publish years, publishers, page counts and subjects. Powered by Open Library (Internet Archive).

api.oanor.com/books-api