[This is preliminary documentation and subject to change.]
Requirement (Designed for Microsoft® Windows® Logo)
If a file name is fully exposed in Microsoft® Windows® Explorer, it must be a fully supported long file name (LFN). Applications are allowed to use "labeling schemes" in which a user is saving, for example, a report type or a game state without actually creating a file that is exposed to the user in Windows Explorer.
See Pretesting UNC and LFN support for a description of pretesting you can do to ensure that your application provides proper UNC and LFN support.