The macOS desktop is a stack of composited layers. The wallpaper is the bottom one — below desktop icons, below every window, below the Dock and menu bar. The window server draws it once and reuses it, which is why a static picture costs essentially nothing.
The layer stack, bottom to top
- Wallpaper layer — your desktop picture or, with a live wallpaper app, a decoded video surface.
- Desktop icons — Finder draws these in their own layer above the wallpaper.
- Application windows — everything you actually work in.
- System UI — menu bar, Dock, Notification Center, Control Center.
Because a live wallpaper only replaces the bottom layer, nothing above it is affected: click-through, window management, screenshots of windows, and Mission Control all behave identically.
Per-display and per-Space
- Each connected display holds its own wallpaper assignment, so different monitors can show different content.
- Spaces can each carry a wallpaper too — a legacy of macOS letting you theme individual desktops.
- Assignments are remembered per display identity. Unplug a monitor, plug it back in, and its wallpaper returns.
Dynamic desktop pictures
Apple's built-in dynamic wallpapers are HEIC files containing several images plus metadata describing which to show for a given sun position or appearance mode. They are still images on a schedule — genuinely useful, but not motion. Video wallpaper is a different mechanism entirely.
The Lock Screen is a separate surface
The Lock Screen and Screen Saver are rendered by the system before your session is unlocked, so an app cannot simply draw into them. Apple added APIs that let apps register a video as a system wallpaper asset in macOS 26 (Tahoe); below that version no third-party app can put motion on the Lock Screen, regardless of what it claims. Once registered, macOS — not the app — plays the loop, which is why applying one takes a moment while the system indexes the asset.
What this means when you pick an app
- Apps that use the real wallpaper layer behave like a native wallpaper. Apps that float a borderless window behind your icons only imitate one — and break with Mission Control, screenshots, and Spaces.
- A native app needs no Screen Recording, Accessibility, or Full Disk Access permission to set a wallpaper. Being asked for those is a signal something unusual is happening.
- MacWall uses the system wallpaper APIs on both surfaces — see Live Lock Screen and Screen Saver.
Keep learning
- What is a live wallpaper?A live wallpaper is a short video loop rendered at the desktop wallpaper layer instead of a still image.
- Hardware video decodeApple's media engine decodes H.264 and HEVC in dedicated silicon, so a 4K wallpaper loop costs almost no CPU.
- Video formats and codecsEncode wallpapers as H.264 or HEVC in an MP4 container, at display resolution, 24–30 fps, with no audio track.
- Resolution and displaysMatch wallpaper resolution to the panel's native pixels, and prefer one mirrored loop over separate loops on every display.
- Battery and energy basicsA wallpaper's battery cost is decode work times time on screen — pausing when nothing is visible removes almost all of it.