Question Does Defender Full Scan check external drives as well as internal?


When I open Windows Explorer and right-click any given drive I have an option to run "Scan with Microsoft Defender....."

Selecting that immediately launches a scan on that drive.

If I cancel the scan then I get another window with four options:

Quick Scan
Full Scan
Custom Scan
Microsoft Defender Offline Scan

At the bottom is a "Scan now" button. I selected "Custom Scan", clicked "Scan now" and a window opened within which I could select what I wanted to scan.

Per @mdd1963 - you will need to simply click and test to determine if the resulting choices and actions meet your requirements.
One would have to imagine/speculate a full scan would hit all connected drives...but, I do indeed see a quick spike in activity via task manager on even my E:drive during a quick scan, but, as there is not much on it, it is difficult to guess what it might be looking for, or how thoroughly.