Mac windows jump when the display arrangement changes.

Mac windows jump when the display arrangement changes because each window's position is stored against that arrangement, not against a fixed desk. Dragging the displays in System Settings, moving the menu bar to a different main display, or connecting a second monitor that macOS places on the other side rewrites those coordinates, so windows land on a different screen or partly off an edge. macOS does not move them back when you correct the diagram. SnapState does not edit the arrangement; after the displays are where you want them, it restores the saved positions and sizes.

Why do Mac windows jump when the display arrangement changes?

In System Settings > Displays, the tiles are not just a picture. macOS builds one coordinate space from them. The display with the menu bar is the origin, and every other display is offset to the left, right, or above. A window frame is a rectangle in that space. When you drag a tile, or drag the menu bar to another display, those offsets change, and the same rectangle now falls on a different screen. That is why every window can jump at once, including apps you did not touch.

This is not the same problem as a new window opening on the wrong screen while the arrangement stays put, or as windows piling up after you unplug a monitor. Those can happen with a stable diagram. Here the diagram itself changed.

What if a second monitor connects with a different arrangement?

Connecting a display does not guarantee the arrangement you used last time. macOS may put the new display on the right by default, restore a stale side from another cable or hub, or keep the menu bar on the laptop. Both monitors are connected, but the windows sit on the wrong relative side because the diagram is different. Setting the arrangement once often sticks for that exact display, and it can fail again when the monitor reports a different identity.

An input switch or a KVM is a different cause: the monitor disappears, which is covered in windows moving when you switch monitor input. Sleep can pile windows onto one screen even when the arrangement never changed. See windows after sleep.

What free fixes should you try first?

• Correct the diagram before you chase windows.In System Settings > Displays, drag the external display to the side you actually use and drag the menu bar onto the display that should be main. The windows will jump again while you do this. That is the coordinate change, not a second bug.
• Drag windows back, or use an app's Window menu. Fine when the arrangement rarely changes.
• Quit and reopen one app only after the diagram is right. Some apps remember the last display. Reopening them while the arrangement is still wrong saves the wrong spot.
• Try Stay. Stay by Cordless Dog has been free since version 1.5.1 and restores window positions for each display setup as displays connect and disconnect. If that covers you, use it. See SnapState vs Stay.

How does SnapState restore windows after an arrangement change?

1. Set the display arrangement you actually want. In System Settings, open Displays and drag the displays into the left, right, or above relationship you use. Drag the menu bar onto the display that should be main. SnapState does not edit this diagram.
2. Arrange the windows and save a named workspace. Put each window where it belongs, then capture the visible desktop from the SnapState menu bar. Name it for that arrangement, such as Office, monitor on the left.
3. Arm matching layout only for that saved arrangement. Turn on the matching display layout trigger if you want a restore when the connected displays match this arrangement again. A different arrangement does not count as a match.
4. Save a separate workspace for a second arrangement. If home puts the monitor above the laptop and the office puts it on the left, save both. Restore the workspace that matches the diagram you just set.
5. Restore by hand when the diagram was wrong. If a second monitor connects on the wrong side, correct System Settings first, then pick the workspace from the menu bar or press its Control-Command-1 to 6 shortcut.

SnapState is a native macOS menu bar app. A workspace stores the visible windows on the current desktop, their positions and sizes, the apps needed to relaunch them, the monitor layout, and the active tab URL of each window in Safari, Chrome, Edge, Brave, Arc, and Chromium once Automation permission is granted. On restore it compares that saved topology with the displays connected now and remaps frames onto them. It does not write the old coordinates onto a rearranged desktop, and it does not change System Settings. A matching display layout trigger runs only when the arrangement matches the saved one. For the manual path, see restoring a multi-monitor layout with one shortcut.

What are the practical details?

SnapState costs $9.99 as a one-time purchase, with a lifetime license for up to three Macs and a 14-day refund. There is no free trial. Version 2.5.2 requires macOS 15.7 or later on Apple Silicon and Intel Macs and ships as a DMG rather than through the Mac App Store. It needs Accessibility permission to move windows, and workspace data stays on your Mac as JSON in ~/Library/Application Support/SnapState/.

What are the honest limits?

SnapState does not stop macOS from jumping windows while you change the arrangement, and it does not repair a wrong diagram on connect. It saves only the visible windows on the current desktop, so it does not save or restore macOS Spaces. It does not tile or snap windows. Firefox is not supported, and only the active tab URL is restored for each supported browser window. It does not auto-restore on login or restart. It requires macOS 15.7 or later.

What else should you know?

Which other display changes move Mac windows?

Arrangement is one cause. Others are unplugging a monitor, clamshell mode, an ultrawide layout, and saving a window layout you can recall after the displays are right. Moom is the comparison if you wanted tiling instead of a saved layout.