It does not run on macOS, and that is unlikely to change

That is the entire answer to the question as asked, so the rest of this page is about the thing the reader actually wants, which is a moving or an automatically changing background on a Mac. Running Windows in a virtual machine does not help, because the wallpaper would be drawn on the virtual Windows desktop inside a window on your Mac, not on the Mac desktop behind your icons.

What macOS gives you instead

Instead of Wallpaper Engine, macOS gives you three things of its own, and between them they cover most of what people install a third party program for. The first is a plain still picture. The second is a dynamic desktop, an image file that holds several versions of the same scene and swaps between them as the day passes. The third is a set of moving aerial wallpapers that play a slow video loop and then settle on a still frame, shared with the screen saver. None of them import anything from the Steam Workshop, and none of them play a file you supply as video.

ScreenPlay is worth naming because it is open source and it runs on macOS, which makes it the closest structural equivalent rather than a compromise. Wallpaper Engine is a Steam program that plays video, scenes, web pages and shaders on Windows, and the piece of that ScreenPlay reproduces is the video and the web page. The scenes and the catalogue do not transfer.

Changing the desktop picture and the lock screen picture

To change the desktop picture on a Mac, open System Settings, choose Wallpaper, and pick an image or add your own with the button that adds a photo or folder. The lock screen picture is a separate control: recent versions of macOS let the desktop wallpaper and the screen saver share the same image, so changing one can change the other, and separating them means choosing a different source in the Screen Saver settings. Setting a wallpaper on a Mac with more than one display is done per display: macOS assigns each screen its own picture and does not span a single file across two, which is the opposite of the Windows Span option.

Why a Mac wallpaper looks blurry when the file was large

A Mac wallpaper looks blurry because the number macOS reports is not the number of pixels the panel has. A Retina display reports points, and there are two pixels per point in each direction, so a file sized to the reported figure arrives at half resolution and gets enlarged to fill the panel. This is the single commonest cause of a soft wallpaper on an otherwise sharp screen, and it catches anime art harder than photographs because clean line work makes the softening obvious.

The second cause is the crop. macOS fills the screen by default, scaling the picture until it covers the whole desktop and discarding whatever hangs off the proportionally longer axis, unless you pick Fit To Screen or Stretch in the wallpaper settings. A tall portrait image set on a wide panel loses its top and bottom, which is why a composition that looked balanced on a phone arrives on a Mac with the character's head missing. 4K is 3840 by 2160, and a Studio Display at 5120 x 2880 wants more than that again, so even a genuinely large download can be undersized here.

Why a dynamic wallpaper stops moving or stops changing

A dynamic wallpaper stops changing when the condition it keys off is no longer available to it. Apple's dynamic desktops shift with the position of the sun, so they need Location Services enabled to know where the sun is; with location off, they fall back to a fixed time zone estimate or simply stop varying. Locking the system appearance to Light or to Dark also pins some dynamic images to a single frame, because the variant they would otherwise switch to is the one you have ruled out.

A moving wallpaper that has stopped moving is usually the intended behavior rather than a fault. Apple's moving desktop pictures play their loop once, at login or when you select them, and then hold a still frame until something restarts them. If a Mac wallpaper is not moving and you expected continuous motion, the honest answer is that macOS does not offer continuous motion in that slot at all, and no setting turns it on.

Why the wallpaper will not change at all

A Mac wallpaper that refuses to change is nearly always one of four things, and they are worth checking in this order:

• Check whether a profile is managing the machine, because a work or school Mac can have the desktop picture locked by policy.
• Check that the source image still exists, since macOS holds a reference to a file and a picture moved or deleted from its folder leaves the old one on screen.
• Check the per display assignment, because changing the wallpaper on the built in screen does nothing to an external monitor.
• Restart the process that draws the desktop by logging out and back in, which clears the cached copy macOS keeps of the current picture.

None of those four is a size problem, which is the fifth thing to check. The same picture is a different file on every Mac in the table above, and half of the problems that get filed as "the wallpaper is broken" are a file that was correct for a different screen. A live wallpaper is a video your device never stops playing, and macOS does not provide that slot, so a file prepared for one is being used somewhere it cannot behave the way it was built to.

Where to go next

DEVICESYour desktop, your phone and your tablet each want a different wallpaper fileWallpaper sizes by deviceWALLPAPER ENGINEWallpaper Engine is a Steam program that plays things on your desktopWallpaper Engine, explainedLIVE WALLPAPERA live wallpaper is a video your device never stops playingWhat it is and what it costsSCREEN SIZE4K is 3840 by 2160, and most files that claim it are notWhat the number buys