Why windows end up the wrong size
A 27-inch monitor has far more room than a laptop screen. When it disconnects, macOS has to move its windows somewhere that still exists, so they land on the laptop. Windows larger than the laptop screen are shrunk to fit, and several windows end up stacked in the same spot. When the monitor comes back, macOS often doesn't move them back or resize them, so you're left with small windows piled on the wrong screen.
Quick fixes for one window
| Goal | How (macOS Sequoia and later) |
|---|---|
| Fill the screen (without full screen) | Fn Control F, or drag the window to the menu bar |
| Left or right half | Fn Control Left Arrow or Right Arrow |
| Center it | Fn Control C |
| Back to the size before tiling | Fn Control R |
| Resize by hand | Drag any edge or corner of the window |
The green button in a window's top-left corner shows the same options: hold the pointer over it and choose under Move & Resize, or choose Fill.
Move it back to the big monitor first
- Drag the window by its title bar across the screen edge onto the monitor.
- Fill or tile it there with the shortcuts above. Tiling works on whichever display the window is on.
- Check the arrangement if the window won't cross where you expect: System Settings › Displays › Arrange.
Stop it happening every day
- Plug into the same port every time, so macOS sees the same display arrangement.
- Avoid rearranging on the laptop while the monitor is away, if you want macOS's own restore to have a chance.
- Use a layout app. macOS doesn't save window sizes per monitor setup. Apps that do will put every window back at its full size when the monitor returns.