Domain Unique ID (DUID for short) is a permanent identifier for each of the folders in your domain. It remains unchanged even if the folder itself is renamed or moved.

DUIDs allow you to create permanent links to a specific folder that will not break even if your content is reorganized. They also allow you to more easily communicate the location of your secured files. Instead of spelling out the entire path to a specific folder through a series of folder name - you can simply reference a direct link to that folder by utilizing the DUID.

A direct link to a folder is available from the WebApp at the bottom of the File -> Show Info window as pictured below: