How to Stop Apps Opening on the Wrong Display (Mac)

macOS has no "open on display 2" checkbox, but window placement isn't random either: apps reopen windows where they were last closed, and anything without a saved position lands on the main display. Fix those two things and apps stop wandering. Here's the routine, plus how to rescue a window that's opened somewhere you can't see.

First: set the main display deliberately

The main display is where the Dock lives by default, where alerts and dialogs appear, and where apps open when they have no remembered position. If your windows keep appearing on the laptop screen while you work on the big monitor, this is usually why.

1. Open System Settings → Displays.
2. Click Arrange (it appears when more than one display is connected).
3. Drag the small white strip — the menu bar — from one display rectangle onto the monitor you want as primary.

The screens flash, and from now on "default" means that monitor. This works the same on macOS 13, 14, and 15.

Teach each app where it lives

For apps that already have a saved position — on the wrong screen — overwrite it:

1. Open the app and drag its window onto the display you want, sized how you like it.
2. Close the window there (Cmd + W), then quit the app.
3. Reopen it. The new window should appear where you closed the last one.

macOS stores window frames per app, so this one-time ritual sticks for most well-behaved apps. A few apps manage their own window positions and ignore the system's memory — for those, look in the app's own preferences for a window or startup setting.

Pin an app to a display with Spaces

When an app absolutely must live on one monitor, assign it. With Displays have separate Spaces turned on (System Settings → Desktop & Dock, under Mission Control — it's the default), each display runs its own desktops:

1. Put the app's window on the display (and desktop) where it belongs.
2. Right-click its Dock icon → Options → This Desktop.

The app now opens on that desktop — on that display — every time. Choose None in the same menu to undo the assignment.

Rescue a window that opened off-screen

Sometimes a window opens on a display that's no longer connected, or straddles a boundary where you can't grab it. In order of effort:

• Click the app so it's frontmost, then choose Window → Zoom — zooming pulls the window into the visible area of the current display.
• On macOS 15, press fn + Ctrl + F (Fill) to snap the front window into the screen you're on.
• Open System Settings → Displays → Arrange and drag the display rectangles — changing the arrangement forces macOS to re-place windows that fall outside any screen.
• As a last resort, unplug the external display; every window jumps to the built-in screen, where you can re-home it properly.

Why dialogs and full-screen apps play by different rules

Two window types ignore the app's remembered position, which is worth knowing before you blame the app. Dialogs and alerts generally follow either their parent window or the main display — if stray alerts keep landing on the wrong screen, that's another vote for setting the main display deliberately. Full-screen windows are Spaces, not windows: they reopen on whichever display's Space they occupied. If a full-screen app keeps claiming the wrong monitor, take it out of full screen, move the window across, and make it full screen again on the display you want — that display now owns its Space.