The INDB file format is a proprietary file type developed by Adobe Systems specifically for use within Adobe InDesign. It serves as a container or 'book' file that manages a collection of individual InDesign documents (INDD files). Instead of forcing a user to maintain a single, massive file for a long document—such as a book, a technical manual, or a lengthy report—the INDB format allows users to link multiple separate chapters or sections together. This modular approach significantly improves performance, reduces the risk of file corruption, and allows multiple contributors to work on different chapters simultaneously. The INDB file keeps track of page numbering, chapter order, table of contents generation, and index synchronization across all included documents. When a user makes changes to the book file, such as reordering chapters or updating styles, those changes are propagated across the linked documents, ensuring consistency throughout the entire publication project.