Mac windows move when an iPad Sidecar display connects or drops.

When you use an iPad as a second display with Sidecar, macOS treats it like any other monitor. If Sidecar ends or the connection drops, macOS moves the iPad windows onto the Mac screen, and it usually does not move them back when the iPad reconnects. Free fixes can make the connection steadier. If windows still end up in a pile, SnapState can restore a saved layout automatically when the display setup changes.

Why do Mac windows move when Sidecar connects or disconnects?

Sidecar turns the iPad into a real extended display. macOS adds it to the display arrangement in System Settings > Displays, and windows you drag onto it belong to that display. When the iPad display disappears, whether you ended Sidecar, the iPad locked or ran low on battery, or a wireless connection dropped, macOS generally moves those windows onto a display that is still connected so nothing is stranded off screen.

When Sidecar connects again, macOS sees a new display connection. It does not reliably send each window back to the iPad or to its earlier position, and adding or removing a display can also nudge windows on your other screens. It is the same behavior as windows moving after you unplug a monitor and windows jumping when the display arrangement changes, just triggered by the iPad. If your windows pile up after the Mac sleeps instead, see windows moving to one screen after sleep.

What free fixes should you try first?

These are worth trying before you pay for anything. Results vary by Mac, iPad, and network.

• Use a cable. Sidecar can run over a USB connection to the iPad, which is usually steadier than a wireless link and keeps the iPad charging.
• Keep the iPad awake and close. Keep the iPad charged, near the Mac, and on the same network, so it is less likely to lock or drop the wireless connection mid-session.
• End Sidecar on purpose.Disconnect from Control Center or System Settings > Displays when you are done, and move the windows you care about off the iPad first, rather than letting it sleep and take the windows with it.
• Send windows to the iPad quickly. Hover over a window green button and choose the option to move it to the iPad, which is faster than dragging each window across after a reconnect.
• Check the arrangement.In System Settings > Displays, place the iPad where it sits on your desk and confirm the main display is the one you expect, so the layout is consistent each time the iPad joins.
• Try Stay. Stay by Cordless Dog has been free since version 1.5.1. It stores window positions for each display combination and can restore them as displays connect and disconnect. See SnapState vs Stay for how the two differ.

How does SnapState put windows back after Sidecar reconnects?

1. Connect the iPad with Sidecar and arrange your windows. With the iPad showing as a display, put each window on the Mac screen, any external monitor, or the iPad, exactly where you want it to come back.
2. Save the arrangement as a named workspace. Capture the setup from the SnapState menu bar app and name it something like Desk with iPad. It records window positions and sizes, the apps to relaunch, the browser tabs in supported browsers, and the display layout.
3. Save a second workspace without the iPad. Disconnect Sidecar, arrange windows the way you like them on the Mac alone, and save that as its own workspace, so each setup has a layout to return to.
4. Arm the monitor connect or matching display layout trigger. Turn on the monitor connect or matching display layout trigger for each workspace. When the iPad reconnects, or when you are back to the Mac alone, SnapState restores the workspace that fits the displays you have now.
5. Restore by hand whenever you want. If a reconnect still leaves things out of place, 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 captures the windows on every Space and every display macOS reports, including an iPad running Sidecar, with their position and size, the apps needed to relaunch them, the display layout, and all open tabs of each window in Safari, Chrome, Edge, Brave, Arc, and Chromium once Automation permission is granted. If the iPad is missing, saved window frames are remapped onto the displays you have now.

The same approach helps if your windows rearrange when you connect a dock or external monitor or close the MacBook lid in clamshell mode.

What are the practical details?

SnapState costs $9.99 as a one-time purchase, with a lifetime license for up to three Macs. Version 2.7.2 requires macOS 15.7 or later on Apple Silicon and Intel Macs and ships as a signed, notarized DMG rather than through the Mac App Store. It needs Accessibility permission to move windows, and workspace data stays local on your Mac as JSON in ~/Library/Application Support/SnapState/.

What are the honest limits?

SnapState does not manage Sidecar itself, so it cannot start the iPad connection or stop it from dropping. It restores layouts across multiple Spaces (apps go back to the Space they were saved on, full-screen windows return to full screen, and windows on other Spaces are placed when you switch to them). Firefox is not supported, and tabs are restored only from supported browsers. It is not a tiling or snapping window manager, and it requires macOS 15.7 or later.

What else should you know?

Where else does this layout break?

The same pile-up happens when a monitor on a USB-C hub reconnects or a DisplayLink dock wakes. One way to put a whole desk back is a multi-monitor shortcut. For tiling rather than restore, see Rectangle, Magnet, and Raycast.