macOS provides the ability to access files stored in the cloud from Finder. This holds for files stored using Apple's iCloud storage solution, but also for third-party cloud storage providers such as Dropbox, Google Drive and Microsoft One Drive. By default these files are only stored in the cloud and their content is only retrieved when needed.

How this works in combination with GrandPerspective is explained below.

How does macOS provide access to "online only" cloud files?

macOS provides the "File Provider" extension for apps to manage files stored in the cloud. From macOS 12.3 onwards this is the only on-demand solution for managing cloud storage. It is used by all major cloud storage solutions on macOS, including iCloud, Google Drive, Dropbox, and One Drive.

Files are by default stored as "online only". This means that they do not take up space on the local disk. To view the contents of such a file, the file is downloaded on demand by macOS. The file contents may then be cached locally so that it is quickly available the next time. When you run out of storage space, macOS will purge these files automatically to free up space.

How to determine how much space the cloud files take up on your disk?

Scan the "CloudStorage" folder using the physical file size measure. As "online only" files take up no space, they are not shown in the resulting GrandPerspective view. The view could therefore contain only a small subset of all files.

How to determine how much space the cloud files take up in the cloud?

Scan the "CloudStorage" folder using the logical file size measure. This typically triggers a warning that the reported size larger than the actual size on disk.

Does scanning cloud storage folders trigger download of files?

No, GrandPerspective only requests file metadata (size, time of last change, etc) from macOS. macOS does not need to download "online only" files to return this information.

However, if the folder was not yet browsed or scanned before, the scan will trigger macOS to create the folder structure locally. This may take some time but does not result in the download of contained files.

How can I ensure that GrandPerspective skips the folders with cloud files when scanning?

For this you can use the filter "No cloud files". When this filter is used the maps containing the cloud files are fully skipped during the scan.

This filter can speed up the scan and is particularly handy when you have many cloud files that are mostly stored online. In that case you can even consider to apply this filter by default. This you do by changing your Preferences.