AppUserModelID (AUMID)

An AppUserModelID (AUMID) is the string Windows uses to identify an application - it controls how windows group on the taskbar, how shortcuts behave, and critically, whether the app's toast notifications appear at all.

Windows only shows notifications for apps it can attribute to a Start Menu shortcut carrying an AUMID. This is the root of the classic Electron mystery: notifications work in development (Electron's own identity is registered) and silently vanish in production, because the packaged app's identity doesn't match any installed shortcut.

The fix is agreement between two places: app.setAppUserModelId('com.company.app') in code, and the same id registered by the installer's shortcut (electron-builder uses the appId field). Test with the real installer - an unpacked .exe has no shortcut, hence no identity, hence no toasts.

The full story, including click handling and the desktop "push" pattern, is in Electron notifications on Windows.