Change "Windows font size (DPI)" in PowerShell?

As supposed in the other answers, the setting under HKLM is not the correct place as the dpi scaling is a user defined setting. The correct registry key is HKCU:\Control Panel\Desktop with the value LogPixels.

More information about all DPI-related registry settings can be found in DPI-related APIs and registry settings.

I wrote a tiny PowerShell script that changes the DPI scaling depending on the current scaling and performs the user logoff, so I just have to execute the script when I put my device to a different monitor.

cd 'HKCU:\Control Panel\Desktop'$val = Get-ItemProperty -Path . -Name "LogPixels"if($val.LogPixels -ne 96){    Write-Host 'Change to 100% / 96 dpi'    Set-ItemProperty -Path . -Name LogPixels -Value 96} else {    Write-Host 'Change to 150% / 144 dpi'    Set-ItemProperty -Path . -Name LogPixels -Value 144}logoff;exit

Apparently you can set the LogPixels property of

HKLM:/Software/Microsoft/Windows NT/CurrentVersion/FontDPI

which is reiterated in a lot of places around the net. However, I got the impression that dpi was a user setting which makes no sense to have under HKLM.

Sorry, I misread the question. I thought you wanted to control the PowerShell windows.

As already mentioned you could set the LogPixels setting in the registry, to see what the current setting is, try this:

Get-Item -Path Registry::'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontDPI' | Select-Object -ExpandProperty Property

If the LogPixels key is there it will show, you can create it if it does not exist:

Set-Item -Path 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontDPI\LogPixels'

NB: You have to run this with privileges that allow you to manipulate the registry.

There is a good introduction to this over at TechNet.