Because it is text-based, IDML is the preferred format for translation agencies using tools like Smartling or Transifex . Top Online INDD to IDML Converters
It is important to note that Because INDD files are complex and proprietary, fully parsing them without the Adobe InDesign engine is difficult for web-based scripts.
These are "online" services, but they utilize actual Adobe InDesign servers in the cloud to process the file. This ensures that formatting, fonts, and layers are preserved perfectly.
100%. Download IDML.