IDML (InDesign Markup Language) is an XML-based format, introduced in Adobe InDesign CS4, for representing InDesign content. IDML is used in several InDesign and InCopy file types:
- IDML files (or packages) are ZIP archives, containing numerous XML files. The entire set of these files represent a complete InDesign document. The files in an archive are described thoroughly in Adobe InDesign CS4 IDML File Format Specification. IDML files are identified by the *.idml file extension.
- Snippets are IDML-based files that describe a subset of an InDesign document. They are not archives, but single XML files that contain IDML. The application UI, scripting facility, and plug-in API allow you to export snippets from InDesign. Most commonly, such a snippet represents a page item or group of page items. These type of snippets usually are identified by the *.inds file extension.
- ICML (InCopy Markup Language) files are a special type of snippet. An ICML file represent s a single InCopy story using IDML. ICML files use the *.icml file extension.
- InCopy assignment files are another type of IDML snippet. They are used to allow multiple writers to work on one InDesign document. Assignment files use the *.icma extension.
- There are other features that leverage IDML; for example, exporting preflight profiles produces an IDML-based file.