AddReg

AddReg is a section in Windows INF files used by the Windows setup and driver installation framework to create or modify registry entries during installation. It enables an installer to provision configuration data and component registration that applications rely on after setup.

Structure: Each entry in an [AddReg] section specifies a registry hive/root (for example, HKLM, HKCU, or HKCR), a full registry key path, a value name, and the data to be written. The data can be a string, a DWORD, a multi-string, or binary, and may include installer-time tokens that are substituted when the package is applied. Multiple entries are supported within a single AddReg section.

Scope: Values written under HKLM affect all users on the machine, while HKCU writes per-user settings. The root and key paths must exist or be created by the installer; the AddReg directive will typically create them as needed in many cases.

Uninstallation: To remove registry entries added by AddReg, installers commonly provide a DelReg section that mirrors the AddReg entries or uses registry cleanup rules during uninstall.

Usage notes: AddReg is part of INF-based installers (such as those used by legacy setup programs and driver packages). It is not used by Windows Installer (MSI) packages, which use their own registry operations. When designing AddReg entries, consider scope, permissions (machine vs user), and the need for cleanup during uninstall. Tokens can refer to version numbers and paths to support flexible deployments.

See also: INF file structure, DelReg, DefaultInstall, AddSection.