Control use of the Serial API

Computer and userIntune-readyDefaultSerialGuardSetting

Supported on Microsoft Edge version 86, Windows 7 or later

155.0.4283.62

What it does

Set whether websites can access serial ports. You can completely block access or ask the user each time a website wants to get access to a serial port. Setting the policy to 3 lets websites ask for access to serial ports. Setting the policy to 2 denies access to serial ports. You can override this policy for specific URL patterns by using the 'SerialAskForUrls' (Allow the Serial API on specific sites) and 'SerialBlockedForUrls' (Block the Serial API on specific sites) policies. If you don't configure this policy, by default, websites can ask users whether they can access a serial port, and users can change this setting. Policy options mapping: * BlockSerial (2) = Do not allow any site to request access to serial ports via the Serial API * AskSerial (3) = Allow sites to ask for user permission to access a serial port Use the preceding information when configuring this policy.

What it writes

Hive: HKEY_LOCAL_MACHINE or HKEY_CURRENT_USER
Registry key: Software\Policies\Microsoft\Edge

Options

Option	Type	Registry value	Allowed values
Control use of the Serial API	Drop-down list	`DefaultSerialGuardSetting`	Do not allow any site to request access to serial ports via the Serial API`2` Allow sites to ask for user permission to access a serial port`3`

Configure and deploy

Choose a state and the option values; the output below is generated from the template for exactly that.

Enabled · Computer · template defaults

Registry file (.reg)

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Edge]
"DefaultSerialGuardSetting"=dword:00000002

PowerShell

$ErrorActionPreference = 'Stop'

function Set-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $PropertyType,
        [Parameter(Mandatory = $true)][object] $Value
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        New-Item -Path $Path -Force | Out-Null
    }

    New-ItemProperty -LiteralPath $Path -Name $Name -PropertyType $PropertyType -Value $Value -Force | Out-Null
}

function Remove-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (Test-Path -LiteralPath $Path) {
        Remove-ItemProperty -LiteralPath $Path -Name $Name -Force -ErrorAction SilentlyContinue
    }
}

function Clear-RegistryKeyValues {
    param(
        [Parameter(Mandatory = $true)][string] $Path
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return
    }

    foreach ($propertyName in (Get-Item -LiteralPath $Path).Property) {
        Remove-ItemProperty -LiteralPath $Path -Name $propertyName -Force -ErrorAction SilentlyContinue
    }
}

# Policy: Control use of the Serial API
# Name: DefaultSerialGuardSetting
# Scope: Machine
# State: Enabled
# Source: msedge.admx

Set-RegistryValue -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Edge' -Name 'DefaultSerialGuardSetting' -PropertyType 'DWord' -Value 2

The OMA-URI is an inferred ADMX-backed Policy CSP candidate derived from the source ADMX file name and policy name.
Some Microsoft policies use built-in Policy CSP pages whose area names don't match the ADMX file name, so verify the candidate against Microsoft Learn before deployment.
The generated payload is incomplete because one or more ADMX element values were not supplied: DefaultSerialGuardSetting

ADMX profile candidate (OMA-URI)

./Device/Vendor/MSFT/Policy/Config/ADMX_msedge/DefaultSerialGuardSetting

Intune remediation scripts

Detection

$ErrorActionPreference = 'Stop'
$reasons = [System.Collections.Generic.List[string]]::new()

function Test-RegistryValueExists {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return $false
    }

    return $null -ne (Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction SilentlyContinue)
}

function Test-RegistryValueEquals {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $Kind,
        [Parameter(Mandatory = $true)][object] $Expected
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return $false
    }

    $valueObject = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction SilentlyContinue
    if ($null -eq $valueObject) {
        return $false
    }

    $actual = $valueObject.$Name
    switch ($Kind) {
        'String' { return [string]$actual -ceq [string]$Expected }
        'ExpandString' { return [string]$actual -ceq [string]$Expected }
        'DWord' { return [uint32]$actual -eq [uint32]$Expected }
        'QWord' { return [uint64]$actual -eq [uint64]$Expected }
        'MultiString' {
            $actualArray = @($actual)
            $expectedArray = @($Expected)
            if ($actualArray.Count -ne $expectedArray.Count) { return $false }
            for ($index = 0; $index -lt $actualArray.Count; $index++) {
                if ([string]$actualArray[$index] -cne [string]$expectedArray[$index]) { return $false }
            }
            return $true
        }
        'Binary' {
            $actualArray = [byte[]]$actual
            $expectedArray = [byte[]]$Expected
            if ($actualArray.Length -ne $expectedArray.Length) { return $false }
            for ($index = 0; $index -lt $actualArray.Length; $index++) {
                if ($actualArray[$index] -ne $expectedArray[$index]) { return $false }
            }
            return $true
        }
        default { return [string]$actual -ceq [string]$Expected }
    }
}

# Policy: Control use of the Serial API
# Name: DefaultSerialGuardSetting
# Scope: Machine
# State: Enabled
# Source: msedge.admx

$isMatch = Test-RegistryValueEquals -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Edge' -Name 'DefaultSerialGuardSetting' -Kind 'DWord' -Expected 2
if (-not $isMatch) {
    $reasons.Add('Value mismatch: HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Edge\DefaultSerialGuardSetting') | Out-Null
}

if ($reasons.Count -eq 0) {
    Write-Output 'Compliant'
    exit 0
}

$reasons | ForEach-Object { Write-Output $_ }
exit 1

Remediation

$ErrorActionPreference = 'Stop'

function Set-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $PropertyType,
        [Parameter(Mandatory = $true)][object] $Value
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        New-Item -Path $Path -Force | Out-Null
    }

    New-ItemProperty -LiteralPath $Path -Name $Name -PropertyType $PropertyType -Value $Value -Force | Out-Null
}

function Remove-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (Test-Path -LiteralPath $Path) {
        Remove-ItemProperty -LiteralPath $Path -Name $Name -Force -ErrorAction SilentlyContinue
    }
}

function Clear-RegistryKeyValues {
    param(
        [Parameter(Mandatory = $true)][string] $Path
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return
    }

    foreach ($propertyName in (Get-Item -LiteralPath $Path).Property) {
        Remove-ItemProperty -LiteralPath $Path -Name $propertyName -Force -ErrorAction SilentlyContinue
    }
}

# Policy: Control use of the Serial API
# Name: DefaultSerialGuardSetting
# Scope: Machine
# State: Enabled
# Source: msedge.admx

Set-RegistryValue -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Edge' -Name 'DefaultSerialGuardSetting' -PropertyType 'DWord' -Value 2

History 37 retained releases

150.0.4078.8016 Jul 2026
- Already present in the first release ChangeIntel keeps.

36 later releases left it unchanged.

Template

Internal name: DefaultSerialGuardSetting
Namespace: Microsoft.Policies.Edge
Template file: msedge.admx
Release: Microsoft Edge 155.0.4283.62 · file set 0a733b0040dbbf02…

Definition, editor controls and support

Definition

<policy class="Both" displayName="$(string.DefaultSerialGuardSetting)" explainText="$(string.DefaultSerialGuardSetting_Explain)" key="Software\Policies\Microsoft\Edge" name="DefaultSerialGuardSetting" presentation="$(presentation.DefaultSerialGuardSetting)" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="Microsoft.Policies.Edge:microsoft_edge" />
      <supportedOn ref="Microsoft.Policies.Edge:SUPPORTED_WIN7_V86" />
      <elements>
        <enum id="DefaultSerialGuardSetting" valueName="DefaultSerialGuardSetting">
          <item displayName="$(string.DefaultSerialGuardSetting_BlockSerial)">
            <value>
              <decimal value="2" />
            </value>
          </item>
          <item displayName="$(string.DefaultSerialGuardSetting_AskSerial)">
            <value>
              <decimal value="3" />
            </value>
          </item>
        </enum>
      </elements>
    </policy>

Editor controls

<presentation id="DefaultSerialGuardSetting" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions"><dropdownList refId="DefaultSerialGuardSetting">Control use of the Serial API</dropdownList></presentation>

Supported platforms and category

Microsoft.Policies.Edge:category:microsoft_edge
<category displayName="$(string.microsoft_edge)" name="microsoft_edge" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
Microsoft.Policies.Edge:definition:SUPPORTED_WIN7_V86
<definition displayName="$(string.SUPPORTED_WIN7_V86)" name="SUPPORTED_WIN7_V86" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
Microsoft.Policies.Edge:category:microsoft_edge
<category displayName="$(string.microsoft_edge)" name="microsoft_edge" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
<strings><string id="Microsoft.Policies.Edge:microsoft_edge">Microsoft Edge</string></strings>
Microsoft.Policies.Edge:definition:SUPPORTED_WIN7_V86
<definition displayName="$(string.SUPPORTED_WIN7_V86)" name="SUPPORTED_WIN7_V86" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
<strings><string id="Microsoft.Policies.Edge:SUPPORTED_WIN7_V86">Microsoft Edge version 86, Windows 7 or later</string></strings>