Define the maximum size of downloaded files and attachments to be scanned: registry value IOAVMaxSizeComputerHKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection

Policy ID: RealtimeProtection_IOAVMaxSize
Scope: Computer Configuration
Supported on: At least Windows Server 2012, Windows 8 or Windows RT
Source: Administrative Templates (.admx) for Windows 11 2026 Update (26H2) (version 1.0)
Category: Windows Components › Microsoft Defender Antivirus › Real-time Protection

Registry

IOAVMaxSize

-Computer

HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection Current key

IOAVMaxSize

REG_DWORDComputer

HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection Current key

Enabled value: Depends on the option value
Element: Define the maximum size of downloaded files and attachments to be scanned
Value type: REG_DWORD
Minimum value: 0
Maximum value: 10000000

Apply with .reg · CMD · PowerShell

.reg

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows Defender\Real-Time Protection]

; Value names and types follow the ADMX. Replace <enter value> below with your own data
"IOAVMaxSize"=dword:<enter value>

CMD

:: Value names and types follow the ADMX. Replace <enter value> below with your own data

reg add "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "IOAVMaxSize" /t REG_DWORD /d "<enter value>" /f

PowerShell

# Value names and types follow the ADMX. Replace <enter value> below with your own data

New-Item -Path 'HKLM:\Software\Policies\Microsoft\Windows Defender\Real-Time Protection' -Force | Out-Null
New-ItemProperty -Path 'HKLM:\Software\Policies\Microsoft\Windows Defender\Real-Time Protection' -Name 'IOAVMaxSize' -PropertyType DWord -Value '<enter value>' -Force | Out-Null