# windowDidChangeBackingProperties(_:) Tells the delegate that the window backing properties changed. ``` @MainActor optional func windowDidChangeBackingProperties(_ notification: Notification) ``` ## Parameters `notification` A notification named `NSWindowDidChangeBackingPropertiesNotification`. ## Discussion You can retrieve the `NSWindow` object in question by sending to `notification`. The notification `NSWindowDidChangeBackingPropertiesNotification` is posted in macOS 10.7.3 or later when a window’s backing scale factor or its color space changes. You should watch for this notification instead of `NSWindowDidChangeScreenProfileNotification` if your app runs on a system version on which the backing properties notification is available. Many apps won’t have the need to watch for this notification, but those that perform sophisticated color handling or manually manage their own cache of window-resolution or color-space-appropriate bitmapped images will find this notification useful as a prompt to invalidate caches or schedule other reassessment for the new resolution or color space. The notification’s `userInfo` dictionary specifies the window’s previous backing scale factor (retrieved with the key`NSBackingPropertyOldScaleFactorKey`) and color space (retrieved with the key `NSBackingPropertyOldColorSpaceKey`). You can compare these with the window’s new previous backing scale factor and color space at the time of the notification to determine which properties changed. --- Copyright © 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)