What does Displays have separate Spaces do on a Mac?

The setting lives in System Settings › Desktop & Dock, in the Mission Control section, under the same name on macOS 14 Sonoma through macOS 27. Most of what it changes shows only with two or more displays, but Stage Manager, and window tiling on macOS 26, need it on even with one display. Changing it takes a log out.

What it does

Apple's one-line description in its Desktop & Dock settings guide is “Set up separate spaces for each display”. Spaces are the extra desktops you create in Mission Control, and full-screen apps get one each. The setting decides whether each display keeps a row of spaces of its own, or whether all your displays move together as one big desktop.

The Stage Manager and window tiling rows apply with one display too; the others show only when you have two or more. The main display is the one you choose in System Settings › Displays, with Use as or by dragging the menu bar in Arrange (Displays settings).

With it on

Each display behaves like a desktop of its own. Swipe or press ⌃→ to change desktop, and only the display you're working on moves; the others stay on what they're showing. Put a video in full screen on your external display and it takes that display only, while you keep working on the other. Apple's Mission Control guide adds that if you enter Mission Control on a second display, only the windows and spaces on that display are shown.

Every display gets a menu bar, and Apple's guides for macOS 15 and later say the Dock is available on all displays, so you don't have to go back to the main screen to reach either. The trade-off is that a window belongs to one display at a time: drag it so it hangs over the edge, and the part on the other display isn't shown. To put a window on the other screen, move it all the way across; how to move a window to another monitor has the ways to do it.

If the ⌘Tab app switcher keeps appearing on the display you're not looking at, that's a separate question. Flick's panel, for one, opens on the display with the pointer or the one with your active window, whichever you choose: see which display Flick opens on.

With it off

Your displays become one wide desktop with one set of spaces. The menu bar and the Dock stay on the main display, and switching desktop changes all your displays together. In exchange, a window can span the gap between two displays and show on both, which is the reason to turn the setting off: a long timeline or a wide spreadsheet across a pair of monitors.

What you give up, according to Apple's Desktop & Dock guide: Split View on your other displays, and Stage Manager, both need the setting on. Apple's macOS 14 guide mentions only Split View, but the setting has the same name and place there.

Stage Manager needs it

If Stage Manager's switch is dimmed in System Settings, this setting is off. Apple's Stage Manager guide says so for macOS 15 and later: if you can't turn on Stage Manager, turn on Displays have separate Spaces. More on it in Stage Manager on a Mac.

• Split View on any display other than the main one needs it too, on every version (Apple's Split View guide). See how to use Split View.
• Window tiling: on macOS 26, System Settings says that window tiling requires Displays have separate Spaces. Apple's tiling guides don't mention it. See how to tile windows.

Changing it

1. Open Desktop & Dock settings

   Choose Apple menu › System Settings, then click Desktop & Dock in the sidebar. You may need to scroll down.

2. Switch the setting

   Scroll to the Mission Control section and turn Displays have separate Spaces on or off.

3. Log out and back in

   The change takes effect after you log out: choose Apple menu › Log Out, then log in again. On macOS 26, System Settings marks the setting Requires log out.

Which to choose

Leave it on, the default, if you use full-screen apps or Split View on an external display, use Stage Manager or window tiling, or want a menu bar and Dock wherever you're working. It's also the safer choice if you aren't sure: more of macOS depends on it.

Turn it off if you need one window to stretch across two displays, or you like all your displays to change desktop together as one surface. You'll reach for the main display's menu bar more often, and Stage Manager and Split View on other displays are off the table until you turn it back on.

With Flick

Flick, the window switcher we make, keeps one list for all your displays: hold ⌥ and tap Tab, and windows from every display and every desktop are there, and picking one brings it forward where it is. The panel opens on the display with the pointer, or, if you set Show switcher on to Display with the active window in Flick's Settings › Appearance, on the display with the window you used last.

With Show only the active Space turned on in Settings › General, Flick counts the desktop showing on each display, so windows on every display you can see stay in the list. And Move pointer to the window after switching sends the pointer to the window you picked when it's on another display. Flick doesn't move windows between displays; it switches to them.

Set up Flick for more than one display