Does windows switch hard drives once another is filled?

[strengthusa]

If I installed Windows 10 on an ssd and fill up the ssd, will windows automatically start placing my files in my hdd?

 

[clarkjd]

No.

 

[USAFRet]

If I installed Windows 10 on an ssd and fill up the ssd, will windows automatically start placing my files in my hdd?

No.
Nor should it. You, the human, need to be smarter than the PC.