ION (File Description File)
The ION System file format
ION files are usually found on Windows computers. They contain textual, human-readable information and descriptions about other files. Specifically, ION files contain content descriptions of other files found on the same machine. The information inside the ION file includes the other files’ name, extension, and different meta information. The file system manager is using ION files to get more information about other files it is using. Other software programs may also use them in order to organize files.
Technical details of ION files
Oftentimes, ION files are named “description.ion” with the respective file extension. They have been around for a long time, which is the reason why older programs such as bulletin board systems also recognize them. Many programs use ION files for different purposes. Thus, their content may differ between the programs that use the ION files. XnView, for example, uses ION files for importing or exporting metadata of different files in the program.