Enable strict MIME type checking for worker scripts
Verified with Microsoft Edge 152.0.4191.53 — updated on September 2, 2026
Supported on: Microsoft Edge version 150, Windows 7 or later
Path in the GPO console
Computer Configuration\Administrative Templates\Microsoft Edge User Configuration\Administrative Templates\Microsoft Edge Description
This policy controls whether strict MIME type checking is used for worker scripts. If you enable or don't configure this policy, worker scripts use strict MIME type checking for JavaScript. Worker scripts that use legacy MIME types are rejected. If you disable this policy, worker scripts use lax MIME type checking. This allows worker scripts that use legacy MIME types, such as text/ascii, to continue to load and run. Browsers traditionally used lax MIME type checking, which allowed JavaScript resources to load with several legacy MIME types. This behavior can create security risks by allowing resources to load as scripts when they weren't intended to be used that way. Microsoft Edge uses strict MIME type checking by default. Enabling this policy follows the default behavior. Disabling this policy lets admins temporarily retain the legacy behavior for compatibility. For more information about JavaScript and ECMAScript media types, see https://html.spec.whatwg.org/multipage/scripting.html#scriptingLanguage.
Registry
Software\Policies\Microsoft\Edge Software\Policies\Microsoft\Edge Value name: StrictMimetypeCheckForWorkerScriptsEnabled
Enabled: StrictMimetypeCheckForWorkerScriptsEnabled = 1
Disabled: StrictMimetypeCheckForWorkerScriptsEnabled = 0
Export Builder
BETAConfigure the state, scope and options, then generate .reg, PowerShell, Intune and SCCM outputs — or add the setting to a multi-setting collection.
These exports write the registry — this is not a managed GPO. ⓘ
Applying both scopes creates an ambiguous configuration (computer takes precedence over user). Only do this intentionally.
.reg file
Windows Registry Editor Version 5.00
; Exported from gporais.com
; Policy: Enable strict MIME type checking for worker scripts
; State: Enabled
; Scope: Computer (HKLM)
; Supported on: Microsoft Edge version 150, Windows 7 or later
[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Edge]
"StrictMimetypeCheckForWorkerScriptsEnabled"=dword:00000001More formats (PowerShell, Intune, SCCM)
PowerShell
# Exported from gporais.com
# Policy: Enable strict MIME type checking for worker scripts
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Microsoft Edge version 150, Windows 7 or later
$path = 'HKLM:\Software\Policies\Microsoft\Edge'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'StrictMimetypeCheckForWorkerScriptsEnabled' -Value 1 -Type DWordIntune XML
No direct Policy CSP / OMA-URI mapping for this policy. Use the Intune Remediation tab, or ingest the ADMX in Intune.Intune Remediation
# === Detection script ===
# Exported from gporais.com
# Policy: Enable strict MIME type checking for worker scripts
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Microsoft Edge version 150, Windows 7 or later
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
$checks = @(
(Test-RegistryValue -Path 'HKLM:\Software\Policies\Microsoft\Edge' -Name 'StrictMimetypeCheckForWorkerScriptsEnabled' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Enable strict MIME type checking for worker scripts
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Microsoft Edge version 150, Windows 7 or later
$path = 'HKLM:\Software\Policies\Microsoft\Edge'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'StrictMimetypeCheckForWorkerScriptsEnabled' -Value 1 -Type DWordSCCM scripts
# Exported from gporais.com
# Policy: Enable strict MIME type checking for worker scripts
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Microsoft Edge version 150, Windows 7 or later
# SCCM Configuration Item guidance:
# Create a Configuration Item of type "Setting: Script".
# Discovery script: use the Detection script below.
# Remediation script: use the Remediation script below.
# Compliance rule: the Discovery script output equals 'Compliant'.
# === Detection script ===
# Exported from gporais.com
# Policy: Enable strict MIME type checking for worker scripts
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Microsoft Edge version 150, Windows 7 or later
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
$checks = @(
(Test-RegistryValue -Path 'HKLM:\Software\Policies\Microsoft\Edge' -Name 'StrictMimetypeCheckForWorkerScriptsEnabled' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Enable strict MIME type checking for worker scripts
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Microsoft Edge version 150, Windows 7 or later
$path = 'HKLM:\Software\Policies\Microsoft\Edge'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'StrictMimetypeCheckForWorkerScriptsEnabled' -Value 1 -Type DWordBuilding a multi-setting collection? Add this setting and generate combined .reg / PowerShell / GPO scripts.