INDD forms the native file extension for projects created in Adobe InDesign, the industry standard for desktop publishing. INDD files contain page layout information, including formatted text, linked images, styles, and swatches. They are used for creating professional publications like magazines, books, brochures, and digital layouts. Sample INDD files are used to test desktop publishing workflows. Developers use them to verify that page layouts are rendered correctly and that linked assets are properly resolved. They are also used to test deep inspection tools that need to extract text or metadata from complex layout files.