Question / Problem
Can I use TreeSize to scan the file system of a mobile phone, which is connected via USB? I can browse the files on the device using the Windows Explorer.
Answer / Solution
In general, TreeSize can scan any systems that have a drive letter assigned in Windows. This typically applies to local drives, network shares, etc.
Most mobile devices will announce themselves as MTP (media transfer protocol) devices, which allows access via Windows Explorer without having an actual drive letter assigned. In this mode, TreeSize cannot scan the contents of the device.
To scan the contents of your mobile device you should check if your mobile device provides a "mass storage usb mode" when being connected to a PC. In this mode, the mobile device will be treated as a regular USB device by Windows and therefore having assigned a drive letter. This will allow TreeSize to scan the device.
Given that your mobile device uses a memory card, you can also use a memory card reader which usually provides the content of the card as a device that can be processed by TreeSize.