Registry

Write Windows registry keys and values during install.

Applies to: MSI and MSIX.

MSIX writes are virtualized. They go into the MSIX package's private registry view, not the live system hive. MSI writes go to the live registry.

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Properties

Property	Type	Required	Default	Description
key	string	yes	–	Full registry key path. Must start with HKEY_CLASSES_ROOT, HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE, HKEY_USERS, or HKEY_CURRENT_CONFIG.
name	string	no	–	Value name. Use null or empty string for the default value of the key.
type	string	no	String	One of String, ExpandString, Binary, DWord, MultiString, QWord.
value	string	no	–	The value. Format depends on type (see below).

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Value formats by type

type	Encoding
String	A regular UTF-16 string.
ExpandString	A binary value containing environment variables to be expanded at read time, e.g., "25,00,50,00,52,00,4f,00,47,00,52,00,41,00,4d,00,46,00,49,00,4c,00,45,00,53,00,25,00,5c,00,4d,00,79,00,20,00,41,00,70,00,70,00,6c,00,69,00,63,00,61,00,74,00,69,00,6f,00,6e,00,00,00".
Binary	Hex-encoded bytes, e.g., "4d,79,41,70,70,6c,69,63,61,74,69,6f,6e".
DWord	32-bit value as 8 hex digits (no 0x). To store decimal 12345 write "00003039" (the same way it appears in .reg exports as dword:00003039).
QWord	64-bit value as 16 hex digits.
MultiString	A binary value containing multiple strings, e.g., "4d,00,79,00,00,00,41,00,70,00,70,00,6c,00,69,00,63,00,61,00,74,00,69,00,6f,00,6e,00,00,00,00,00"

Source of the rule: Registry values for non-string types follow the same format as in the output of a Windows .reg file. If regedit exports your value as dword:00003039, you write 00003039.

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Default value of a key (the (Default) entry)

To create or set the default value of a key, omit name or set it to null / "":

{
  "key":   "HKEY_LOCAL_MACHINE\\SOFTWARE\\My Application",
  "value": "Default value here"
}

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Examples

A typical app config block

"registries": [
  { "key":   "HKEY_LOCAL_MACHINE\\SOFTWARE\\My Application",
    "value": "My Application" },

  { "key":   "HKEY_LOCAL_MACHINE\\SOFTWARE\\My Application",
    "name":  "InstallPath",
    "type":  "ExpandString",
    "value": "25,00,50,00,52,00,4f,00,47,00,52,00,41,00,4d,00,46,00,49,00,4c,00,45,00,53,00,25,00,5c,00,4d,00,79,00,20,00,41,00,70,00,70,00,6c,00,69,00,63,00,61,00,74,00,69,00,6f,00,6e,00,00,00" },

  { "key":   "HKEY_LOCAL_MACHINE\\SOFTWARE\\My Application",
    "name":  "Version",
    "type":  "String",
    "value": "$.version" },

  { "key":   "HKEY_LOCAL_MACHINE\\SOFTWARE\\My Application",
    "name":  "Telemetry",
    "type":  "DWord",
    "value": "00000000" },

  { "key":   "HKEY_LOCAL_MACHINE\\SOFTWARE\\My Application",
    "name":  "TraceLevel",
    "type":  "DWord",
    "value": "00000003" }
]

Per-user setting (HKCU)

{
  "key":   "HKEY_CURRENT_USER\\SOFTWARE\\My Application",
  "name":  "Theme",
  "type":  "String",
  "value": "Light"
}

A multi-string value

{
  "key":   "HKEY_LOCAL_MACHINE\\SOFTWARE\\My Application",
  "name":  "Plugins",
  "type":  "MultiString",
  "value": "4d,00,79,00,00,00,41,00,70,00,70,00,6c,00,69,00,63,00,61,00,74,00,69,00,6f,00,6e,00,00,00,00,00"
}

The \u0000 is the JSON escape for the null character that delimits MultiString entries.

A binary value

{
  "key":   "HKEY_LOCAL_MACHINE\\SOFTWARE\\My Application",
  "name":  "Magic",
  "type":  "Binary",
  "value": "4d,79,41,70,70,6c,69,63,61,74,69,6f,6e"
}

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MSI vs MSIX behavior

Aspect	MSI	MSIX
Writes to live registry	Yes.	No. Writes go into the MSIX package container's virtual hive.
Visible in regedit	Yes (under the actual hive).	Only when running regedit from inside the package's view.

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Validation rules

Validator	Catch
required	key is mandatory.
valid registry key	Must start with one of the five allowed hive prefixes.
valid value	type must be one of the supported registry types.
duplicate registry check	Two entries with the same key + name combination is an error.

You will also see warnings if you write to HKEY_LOCAL_MACHINE outside the recommended HKEY_LOCAL_MACHINE\SOFTWARE and HKEY_LOCAL_MACHINE\SYSTEM keys – Windows packaging best practices want apps to stay in the SOFTWARE hive.

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