If you have access to InDesign, doing this locally is instantaneous and free. It is the recommended workflow:
The INDD (InDesign Document) format is Adobe InDesign’s proprietary file format for professional page layout. The IDML (InDesign Markup Language) format is an XML-based, open-standard representation of an InDesign document. Online converters that transform INDD to IDML serve a critical need: enabling backward compatibility, version interoperability, and recovery of corrupted files. This report examines the technology, use cases, key tools, limitations, and security considerations of INDD-to-IDML online converters. indd to idml online converter
Adobe has integrated file conversion into its cloud ecosystem. If you save your INDD file to the Creative Cloud, you can utilize Adobe’s servers to export an IDML version. If you have access to InDesign, doing this