The short version: Most external-monitor trouble with Rectangle isn’t Rectangle misbehaving — it’s macOS’s display arrangement or scaling feeding it bad information. Windows landing on the wrong screen usually means your arrangement doesn’t match your desk; wrong sizes usually mean mismatched scaling. Both have clean fixes, plus there are dedicated shortcuts for moving windows between displays. Here’s each one.
Windows land on the wrong monitor
The most common complaint, and the cause is almost always the display arrangement in System Settings. Rectangle positions windows based on how macOS believes your monitors are laid out — which screen is left, which is right, where the edges meet. If that arrangement doesn’t match your physical desk, Rectangle’s “move to next display” will send windows somewhere that feels wrong even though the app is doing exactly what it was told.
Open System Settings → Displays and look at the arrangement. Drag the display icons so they match your real setup: if your external monitor sits to the right of your laptop, its icon should be to the right. Line the arrangement up with reality and the wrong-monitor behavior usually resolves on its own, because now Rectangle’s idea of “next display” matches yours.
Moving windows between displays the fast way
If you’re dragging windows from one screen to another and then snapping them, there’s a better way. The Rectangle app has dedicated shortcuts for sending the active window to the next or previous display in one keystroke. If those shortcuts aren’t assigned, set them in Rectangle’s settings.
Once they’re set, moving a window across monitors is instant and predictable — no dragging across the seam between screens, no window getting stuck half on each. If you’re assigning these, it’s a good moment to review your whole shortcut set at once rather than piecemeal; doing it in a single deliberate pass keeps things consistent.
Wrong window sizes on the external screen
If windows move to the right monitor but come out the wrong size there, scaling is the usual reason. Two displays frequently run different scaling, so a “half” on your laptop panel is a different pixel width than a “half” on the external monitor. When one display uses a scaled resolution that doesn’t divide evenly, halves and thirds land a pixel or two off.
Check the external display’s scaling under System Settings → Displays. A resolution that divides cleanly gives more predictable snapping. This is the same underlying cause as general sizing trouble, so if the sizes are off on both screens rather than just the external one, the dedicated writeup on windows snapping to the wrong size goes deeper on gaps and scaling.
Windows scatter when you unplug
This one looks like Rectangle losing your layout, but it’s macOS. When you disconnect an external display, macOS has to put its windows somewhere, so it relocates them onto the remaining screen — often piled up or resized. Rectangle didn’t move them; the disconnect did.
There’s no preventing macOS from doing this, but recovery is fast: once you’re down to one screen, re-snap the windows with your usual shortcuts and the layout is back in seconds. This is exactly where having a few well-practiced shortcuts pays off, and it’s part of why running Rectangle on a Mac that regularly docks and undocks is worth the small setup.
Windows don’t move at all on one display
Separate symptom, separate cause. If shortcuts do nothing on a particular display — or nothing anywhere — that’s not an arrangement or scaling issue. It’s almost always the Accessibility permission or a shortcut conflict, and the fix is different from anything above. The shortcuts not working checklist is the right place for that; this page is specifically about windows that do move but end up on the wrong screen or wrong size.
Getting a stable multi-monitor setup
In order: match the display arrangement to your physical desk, assign the next/previous-display shortcuts, and check that each monitor’s scaling divides cleanly. That trio fixes nearly every external-monitor complaint. The theme underneath all of them is that Rectangle acts on what macOS reports about your displays, so when something looks wrong, the fix is usually in Displays settings rather than in Rectangle itself. Get those aligned and a docking, multi-screen workflow becomes genuinely smooth.
Frequently asked questions
Why does Rectangle move windows to the wrong monitor?
Usually because the display arrangement in System Settings doesn’t match your physical layout. Rectangle moves windows based on how macOS thinks your screens are positioned. Correcting the arrangement so it matches your real desk fixes most wrong-monitor behavior.
How do I move a window to another display with Rectangle?
Rectangle has dedicated shortcuts for moving the active window to the next or previous display. Assign those in Rectangle’s settings if they aren’t set. They move a window across monitors directly, which is faster and more reliable than dragging it between screens.
Why are window sizes wrong on my external monitor?
Different displays often run different scaling, so a half on one screen isn’t the same pixel size as a half on another. If windows land at odd sizes on the external monitor, check that display’s scaling setting; a resolution that divides cleanly gives more predictable halves and thirds.
Why do my windows rearrange when I unplug the monitor?
That’s macOS moving windows off the disconnected display, not Rectangle. When the external screen goes away, macOS relocates its windows to the remaining display. Re-snapping them with Rectangle shortcuts restores your layout quickly once you’re back to one screen.