Custom Actions

The customActions object is a container for six different kinds of custom actions:

"msi": {
  "customActions": {
    "exe":            [ … ],   // run an executable
    "dll":            [ … ],   // call a function in a DLL
    "registerDll":    [ … ],   // regsvr32 a DLL
    "powershell":     [ … ],   // run a .ps1 script (embedded into MSI)
    "installDriver":  [ … ],   // install a driver from .inf
    "setProperty":    [ … ]    // set an MSI property at runtime  ★ NEW in 2.2.0
  }
}

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Common properties

All custom-action types share these common properties:

Property	Type	Required	Default	Description
name	string	yes	–	Unique name within the package.
condition	string	no	–	MSI conditional expression that gates the action.
sequence	string	no	EndOfExecution	StartOfExecution, EndOfExecution, or any short int (-32768 to 32767).
continueOnError	boolean	no	false	If true, install proceeds when the action errors.

Common conditions

Goal	Condition
Always	null
Only during install	NOT Installed
Only during repair	Installed AND NOT REMOVE
Only during uninstall	REMOVE~="ALL"
Only during Windows 11	(VersionNT = 1100 AND MsiNTProductType = 1)
Only during x64 OS	VersionNT64
Only during x86 OS	NOT VersionNT64

Full grammar: Microsoft's Conditional Statement Syntax.

---

exe – run an executable

Property	Type	Required	Description
name	string	yes	Action name.
filePath	string	yes	Path to the executable. Validated as a syntactically valid path. Can be a path inside the package.
arguments	string	no	Arguments.
condition, sequence, continueOnError	–	no	See common.

{
  "exe": [
    {
      "name":      "PostInstallSetup",
      "filePath":  "$.installDir\\My Application.Setup.exe",
      "arguments": "--silent --first-run --language [LANGUAGE]",
      "condition": "NOT Installed",
      "sequence":  "EndOfExecution"
    }
  ]
}

---

dll – call a function in a DLL

Property	Type	Required	Description
name	string	yes	Action name.
filePath	string	yes	Path on disk at build time to the DLL (its bytes are embedded into the MSI).
entryPoint	string	no	Name of the exported function to call.
arguments	string	no	Arguments.
condition, sequence, continueOnError	–	no	See common.

{
  "dll": [
    {
      "name":       "My ApplicationPostInstall",
      "filePath":   "ca\\My Application.CustomActions.dll",
      "entryPoint": "PostInstall"
    }
  ]
}

---

registerDll – regsvr32 a DLL

Property	Type	Required	Default	Description
filePath	string	yes	–	DLL inside the package (validated against fileSystemEntries).
unregisterOnUninstall	boolean	no	true	Whether to regsvr32 /u on uninstall.

{
  "registerDll": [
    { "filePath": "$.installDir\\My CompanyShellExt.dll" }
  ]
}

---

powershell – run a .ps1 script

Property	Type	Required	Description
filePath	string	yes	Path on disk at build time to the .ps1 (its content is embedded into the MSI).
condition, sequence, continueOnError	–	no	See common.

{
  "powershell": [
    {
      "filePath":  "ca\\InitializeDatabase.ps1",
      "condition": "NOT Installed",
      "sequence":  "EndOfExecution"
    }
  ]
}

---

installDriver – install a driver from .inf

Property	Type	Required	Default	Description
filePath	string	yes	–	.inf path inside the package.
importCertificate	boolean	no	false	Import the driver's signing certificate to TrustedPublishers before install.
removeOnUninstall	boolean	no	true	Uninstall the driver when the package is uninstalled.

{
  "installDriver": [
    {
      "filePath": "$.installDir\\drivers\\My CompanyUSB.inf",
      "importCertificate": true
    }
  ]
}

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setProperty – set an MSI property at runtime ★ NEW in 2.2.0

Use this to compute a property value conditionally during install. It is the safe modern way to gate other custom actions.

Property	Type	Required	Default	Description
propertyName	string	yes	–	Property name to set.
propertyValue	string	yes	–	Value to set (supports [Property] substitution).
condition, sequence, continueOnError	–	no	Default sequence is StartOfExecution.

{
  "setProperty": [
    {
      "propertyName":  "INSTALL_TIER",
      "propertyValue": "Enterprise",
      "condition":     "Privileged"
    },
    {
      "propertyName":  "INSTALL_TIER",
      "propertyValue": "Standard",
      "condition":     "NOT Privileged"
    }
  ]
}

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Validation

• unique custom action name – every name across exe, dll, powershell must be unique.

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