Where your Mac windows go in clamshell mode
In clamshell mode the lid is shut and an external display does the work. Every time you open or close that lid, a display leaves or joins the setup, and macOS moves windows to suit. Here is where they go, and what puts them back.
What clamshell mode is
Clamshell mode is a MacBook with the lid closed, running from an external display, usually with a keyboard and mouse attached. The built-in screen is switched off, so it is not part of the display setup any more.
Nothing is broken. The Mac simply has one fewer display for as long as the lid stays shut.
Where your windows go when you close the lid
Any window that was on the built-in display has nowhere to be, so macOS moves it onto the screen that is left, the external monitor. Windows that were already on the external monitor usually stay where they are.
If you had windows spread across both screens, closing the lid gathers them onto the external one.
Where they go when you open it again
The built-in display comes back, and that counts as a display change all over again. macOS sometimes spreads your windows back across both screens and sometimes leaves them piled on the external monitor. How long the lid was shut, and how the displays connect, both affect which happens.
This is the part people notice: they open the lid and half the layout has moved. It looks like a bug and is really macOS doing what it does whenever a monitor appears. Why it happens.
It is a common complaint with no product page answering it. How to stop mac from moving windows from external display to laptop when opening laptop lid is the top result for the search, and Apple's own forum has On wake-up windows have moved from extended to primary, where someone describes the same thing with two external screens and the lid shut.
Lid shut and lid open are two different setups
To a Mac, lid-closed-with-monitor and lid-open-with-monitor are not one arrangement. The built-in display is present in one and absent in the other, so they are two setups.
That is why a tool has to keep two layouts here, not one. A single saved layout cannot be right for both, because a window that sits on the built-in display when the lid is open has to sit somewhere else when it is closed.
What you can do with macOS alone
- Move the windows off the built-in display before you shut the lid. Nothing moves if there is nothing on the screen that is going away.
- Assign apps to the external display. Right-click the app in the Dock, choose Options › Assign To, and pick the monitor, so new windows open there rather than on the laptop.
- Leave the lid open. Then the display setup never changes and no windows move, at the cost of running both screens.
None of these puts the layout back the way it was before the lid closed.
What an app adds
What is missing is a memory of where windows sit with the lid shut and where they sit with it open, and something that puts each one back when that setup returns.
That is what Resettle does. It learns each setup as you work. Lid-closed and lid-open are two separate setups, each with its own layout, and when you open the lid the lid-open layout comes back once the displays have settled. $14.99 once, with a 14-day refund and no free tier.
- Lid shut with an external monitor, and lid open with both screens, are remembered separately.
- Tells identical monitors apart, including the same model at home and at work.
- Nothing to set up. There are no layouts to build or save.
- Full-screen windows go back to full screen on the right display.
Resettle restores windows once a setup is back. It does not stop macOS moving them when the lid opens, and it does not keep one layout for both lid positions.
Questions
Why do windows jump to the external monitor when I close the lid?
Closing the lid switches off the built-in display, so any window that was on it has to go somewhere. macOS moves it to the screen that is left, which is the external monitor.
Why do my windows move when I open the lid again?
The built-in display coming back is a display change. macOS sometimes spreads the windows across both screens again and sometimes leaves them on the external monitor.
Do I need to keep the lid open for Resettle?
No. Resettle treats the lid-shut setup and the lid-open setup separately and keeps a layout for each, so it works in clamshell mode and it works with the lid open.