Stop Windows from Changing Your Default Printer

The default printer carries a flag in the print spooler. A machine that switches on its own shows a different flag after every print job.

Get-Printer | Select-Object Name,PrinterStatus,Type
Get-CimInstance Win32_Printer | Select-Object Name,Default,WorkOffline,Shared
(Get-CimInstance Win32_Printer | Where-Object Default).Name

**LegacyDefaultPrinterMode** toggles the Windows 10 style behaviour. With it set, the last used printer no longer becomes the default.

New-Item 'HKCU:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows' -Force | Out-Null
Set-ItemProperty 'HKCU:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows' -Name LegacyDefaultPrinterMode -Value 1 -Type DWord
Get-ItemProperty 'HKCU:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows' | Select-Object LegacyDefaultPrinterMode

The Settings toggle is the supported switch and it writes the same state. Doing both avoids a surprise when an update resets one of them.

Start-Process ms-settings:printers
# Printers & scanners > Let Windows manage my default printer > Off
Get-ItemProperty 'HKCU:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows' | Select-Object LegacyDefaultPrinterMode

**Set-Printer -Name** makes one printer the default and clears the flag on the others. The change applies to the current user only.

Set-Printer -Name 'HP LaserJet 1020'
Get-CimInstance Win32_Printer | Where-Object Default | Select-Object Name
Get-Printer | Select-Object Name,PrinterStatus | Sort-Object Name

Some apps remember their own printer and ignore the default. A print dialog that keeps offering the PDF printer has its own last-used setting.

Get-ItemProperty 'HKCU:\Software\Microsoft\Windows NT\CurrentVersion\Windows' | Select-Object Device
Get-Content "$env:USERPROFILE\AppData\Roaming\Microsoft\Windows\PrinterPorts" -ErrorAction SilentlyContinue | Select-Object -First 5
Get-PrinterProperty -PrinterName 'HP LaserJet 1020' -ErrorAction SilentlyContinue | Select-Object PropertyName,Value

The test is a restart and a print from two different apps. If the default moves again, a policy or a management agent is overriding the user setting.

Restart-Computer
Get-CimInstance Win32_Printer | Where-Object Default | Select-Object Name
Get-ItemProperty 'HKCU:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows' | Select-Object LegacyDefaultPrinterMode
Get-WinEvent -LogName 'Microsoft-Windows-PrintService/Admin' -MaxEvents 5 -ErrorAction SilentlyContinue | Select-Object TimeCreated,Id,Message -First 2