What is the maximum path / filename length?

The maximum path lengths (including filename) are:

SyncBackV4 and later: approximately 32,767 characters, except when using Zip compression which is approximately 512 characters, and when using the cloud (Microsoft Azure and Amazon S3) the maximum filename length is approximately 1024 characters.

SyncBack V3 freeware: approximately 255 characters.

Note: the path in any error message or log entry may be a relative path (relative to the Source/Left or Destination/Right string, whichever applies). You may need to add the former to the latter to see the total length of the actual full path.

Remember also that the root or home location as used in some protocols (FTP, for example) may in fact point to a directory on the underlying storage with a significant path depth of its own (user-specific subfolders inside a special demarcated area on the actual disk, for example)

Bear in mind also that other services and/or devices may have lower limits, such as FTP servers and NAS devices.