What are NWC and NWF files?
When Navisworks opens a model from another application, such as Revit or AutoCAD, it converts it into an NWC cache file saved next to the source. The next time the model is opened, Navisworks reads the cache instead of converting the file again, as long as the source hasn’t changed. Many authoring tools can also export NWC files directly.
An NWF file is the working file of a coordination project. It stores references to the models that make up the project, whether NWC, NWD or native files, together with review work such as viewpoints, clash tests, comments and redlines, but not the geometry itself. Publishing the project produces a self-contained NWD file.