ISBNLookup.org is a web-based tool that retrieves book information using an International Standard Book Number (ISBN), a unique numeric identifier assigned to books. It queries global bibliographic databases, library catalogs, and retailer APIs to aggregate details such as the title, author, publisher, page count, and cover images. The tool supports both ISBN-10 and ISBN-13 formats and automatically converts between them. The platform includes several features for accessing book data. An AI overview function generates summaries and analyses of books. A barcode scanner allows mobile users to capture a book barcode using their device camera for lookup. The tool accesses a database of over one million books. Typical users include readers, researchers, librarians, and booksellers. The standard workflow involves entering an ISBN or scanning a barcode to receive aggregated information from multiple sources. ISBNLookup.org was developed by Bookllo Publishing LLC. The site includes a disclaimer stating it is not affiliated with Google, the Internet Archive, or the International ISBN Agency, and it notes that it earns from qualifying purchases as an Amazon Associate.