Limit Windows diagnostic data to "Required" by policy — via Microsoft Learn

Group Policy

Open gpedit.msc (Pro, Enterprise and Education only) and go to:

Computer Configuration > Administrative Templates > Windows Components > Data Collection and Preview Builds > Allow Diagnostic Data (Enabled: Send required diagnostic data)

Registry equivalent

Double-click a .reg file and confirm to merge it. Right-click → Edit first if you want to read it, which is always a good idea with any .reg file from the internet.

Apply

Windows Registry Editor Version 5.00

; Oddbyte.Me: Limit Windows diagnostic data to "Required" by policy

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\DataCollection]
"AllowTelemetry"=dword:00000001

Undo

Windows Registry Editor Version 5.00

; Oddbyte.Me: undo Limit Windows diagnostic data to "Required" by policy

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\DataCollection]
"AllowTelemetry"=-

Same thing from a command prompt

Run in an administrator Command Prompt or Terminal.

reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\DataCollection" /v "AllowTelemetry" /t REG_DWORD /d 1 /f

Undo:

reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows\DataCollection" /v "AllowTelemetry" /f

Levels: 0 = diagnostic data off (Security), 1 = Required, 3 = Optional. Microsoft says 0 is honoured only on Enterprise, Education, IoT and Server; on other editions it acts like 1. Microsoft requires optional diagnostic data to run Windows Insider Preview builds, so with this policy on you can't get Insider builds. The policy value takes precedence over the Settings choice.