IdmL

IDML, or InDesign Markup Language, is an XML-based interchange format developed by Adobe for InDesign. It uses the .idml file extension and is stored as a zipped archive containing multiple XML files plus referenced assets. Its purpose is to enable document exchange across InDesign versions and between applications, supporting automated workflows and interoperability.

The IDML structure decomposes a document into components such as designmap.xml, which lists the document’s composition; stories and spreads are represented in separate XML files; styles, swatches, and master pages are defined in dedicated parts; images and other assets are stored as linked files referenced by the XML. This modular organization facilitates programmatic access to typography, layout, and metadata without opening the native InDesign file.

Because IDML is human-readable and text-based, it can be created, modified, or transformed with scripts or XSLT, allowing developers to batch-edit content or styling and to automate publishing workflows without using InDesign directly. IDML is typically generated by InDesign when exporting to IDML and can be imported to reconstruct a document in InDesign, often used to recover, upgrade, or downgrade files across versions.

Limitations and considerations include that some dynamic features, plugins, or effects may not translate perfectly, and assets must be accessible to the importing application. Complex formatting may require adjustments within InDesign after import.

History: Introduced with InDesign CS4 in the late 2000s as an interoperable interchange format, IDML has since remained a core tool for workflow automation, version control, and cross-version document exchange in publishing environments.