<!--
{
  "availability" : [
    "macOS: 10.14.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "AppKit",
  "identifier" : "/documentation/AppKit/NSWindow/appearanceSource",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Property",
  "symbol" : {
    "kind" : "Instance Property",
    "modules" : [
      "AppKit"
    ],
    "preciseIdentifier" : "c:objc(cs)NSWindow(py)appearanceSource"
  },
  "title" : "appearanceSource"
}
-->

# appearanceSource

An object that the window inherits its appearance from.

```
weak var appearanceSource: (any NSAppearanceCustomization)! { get set }
```

## Discussion

The default value of this property is [`NSApp`](/documentation/AppKit/NSApp). The window uses key-value observing to monitor the source’s [`effectiveAppearance`](/documentation/AppKit/NSAppearanceCustomization/effectiveAppearance) for changes. Typically, you use this property for child windows shown from a parent window or specific view.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)