The INX (InDesign Interchange) file format is a legacy XML-based file format developed by Adobe Systems for use with Adobe InDesign. It was primarily designed to allow users to open InDesign documents in older versions of the software, facilitating backward compatibility that was not natively supported by the standard INDD binary format. Because INX files are structured as XML, they are human-readable and can be parsed by external applications to extract text, layout information, and metadata without requiring the full InDesign engine. This made them particularly useful for translation workflows, automated document generation, and third-party plugin development. While Adobe eventually replaced INX with the IDML (InDesign Markup Language) format starting with InDesign CS4, INX remains significant for archival purposes and for users working within legacy publishing environments. It serves as a bridge between different versions of professional desktop publishing software, ensuring that complex page layouts, typography settings, and linked assets remain intact when moving files across different software iterations.