Aside from its major headline-grabbing capabilities, macOS Mojave brought a new Dynamic Desktop feature that automatically adjusts a special wallpaper to match the time of day.
The operating system includes two dynamic wallpapers, one a desert-themed photograph and the other a solar gradient. Both change seamlessly from day to night as time goes on.
A time-shifting desktop wallpaper
Because it needs to know where you live, Dynamic Desktop requires Location Services similar to how Night Shift is based on local sunrise and sunset times. “Dynamic Desktop pictures change throughout the day based on your location,” reads the feature’s description.
For years macOS has included the option to change the desktop wallpaper image every time you log in to your Mac or wake the computer from sleep.
You can also set the wallpaper to change automatically every x minutes, hours or days. This simply cycles through multiple wallpaper images based on your criteria. With Dynamic Desktop, the wallpaper changes subtly and gradually to match the current time in your location.
How to test Dynamic Desktop
Words cannot properly convey the subtleties of Dynamic Desktop. Best thing you experience it yourself by choosing a dynamic wallpaper in your desktop and screen saver preferences.
TUTORIAL: How to use Nigh Shift for Mac
Dynamic Desktop requires specially crafted wallpapers.
How Dynamic Desktop images are packaged
As mentioned earlier, macOS Mojave ships with two dynamic wallpapers that have “Dynamic” in the file name. They’re in addition to the new desert-themed light and dark wallpapers that are used in conjunction with Mojave’s Light and Dark modes.
So what’s the secret sauce to the time-shifting desktop?
Dynamic wallpapers use Apple’s space-saving HEIF image format (.HEIC extension) that launched in September 2017 on iOS 11 and macOS High Sierra. To see all high-resolution wallpaper files on your system, click the Finder’s Go menu and select the option Go to Folder.
Enter the following location and press Return:
The default Mojave dynamic wallpaper is a 114-megabyte HEIC file.
Dynamic Desktop wallpapers are encoded in the space-saving HEIC image file format
By comparison, all of the other wallpapers in Mojave are stored in the ubiquitous JPEG format (each rules file is around ten megabytes in size). Apple currently does not provide any instructions for those wishing to create their own dynamic wallpapers.
So how does that 114-megabyte HEIC file work?
Apple took multiple photographs of the same spot at various intervals between sunrise and dusk to achieve the incredibly smooth transition between day and night. Thanks to enthusiasts, we know that Mojave’s dynamic wallpaper includes 16 layers in one HEIC file.
Feel free to check out each image as a downloadable JPG via GitHub.
But why is it that opening Mojave’s HEIC wallpaper in Preview shows just a single image? That’s because Preview does not support the full range of HEIF features, like packing burst images, multiple shots and more in a single HEIC file.
Mojave’s multi-image HEIC wallpaper file appears as a single image in Preview
What isn’t entirely clear is if users might be able to create their own dynamic wallpapers for Mojave, whether or not doing so would require some special software tools and whether Apple might be planning on detailing Dynamic Desktop in support documents.
Back to your iPhone
iPhone and iPad have included dynamic wallpapers since iOS 7.
iOS’s dynamic wallpapers are not time-shifting HEIC image files like on Mojave. Rather, they’re Quartz Composer-based projects that are programmatically animated and respond to motion.
Aside from still and programmatically animated wallpapers, iOS has provided Live wallpapers since 2015. These things are basically Live Photos that animate on the Lock screen when pressed with 3D Touch (on the Home screen, Live wallpapers look like still images).
Wrapping it all up
I’m a big, big fan of the Dynamic Desktop in macOS Mojave.
Paired with the awesome new Dark Mode, the Dynamic Desktop feature alters the user interface and changes your desktop wallpaper over the course of the day.
Thoughts on Dynamic Desktop?
Meet us in comments!