Drag it
The method that always works: put the pointer on the window's title bar, the strip across the top with the close, minimize and green buttons, and drag it across the edge of the screen into your other display. Which edge connects to which display depends on your arrangement in System Settings › Displays › Arrange. If the window won't cross where you expect, line up the edges there.
If a window is too big to grab comfortably, use the green button's menu or the Window menu to shrink it first, then drag it over.
Make an app open on a specific display
- Turn on separate Spaces. In System Settings › Desktop & Dock, under Mission Control, make sure Displays have separate Spaces is on. You may need to log out and back in for a change to take effect.
- Control-click the app in the Dock. The app should be open or kept in the Dock.
- Choose Options › Assign To › Desktop on Display. Pick the display number you want. The app now opens there.
The Assign To menu also offers All Desktops (the app follows you everywhere) and None (it opens wherever you are).
Arrange the window once it's there
In macOS Sequoia and later, every display supports window tiling:
| Action | How |
|---|---|
| Left or right half | Fn Control Left Arrow or Right Arrow |
| Top or bottom half | Fn Control Up Arrow or Down Arrow |
| Fill the screen (not full screen) | Fn Control F |
| Center | Fn Control C |
| Back to the previous size | Fn Control R |
| Snap by dragging | Drag to a screen edge or corner, or hold Option while dragging |
You can turn the dragging behaviors on or off in System Settings › Desktop & Dock, under Windows: Drag windows to screen edges to tile, Drag windows to menu bar to fill screen, Hold ⌥ key while dragging windows to tile and Tiled windows have margins.
Full-screen windows
A window in full screen lives in its own Space on one display. To move it, exit full screen first (press Fn F or use the green button), drag it to the other display, then make it full screen again.