It is a file format employed by Adobe InDesign. This file type represents an InDesign Markup Language document, essentially a package containing XML-based instructions that define the structure, text, graphics, and formatting of an InDesign layout. As an example, consider a magazine designed in InDesign; saving the project creates a file containing all the visual elements and text arranged on its pages. Converting it to its respective format produces a file that serves as a blueprint for recreating that layout.
Its significance lies in its ability to facilitate the interchange of InDesign documents across different versions of the software. This ensures accessibility and editability even when newer InDesign versions render older files incompatible. The formats introduction marked a pivotal moment in publishing workflows, providing a more robust and open standard compared to proprietary formats. This advancement supports archiving, collaboration, and automation processes within the graphic design and publishing industries.