The short version: Rectangle works out which display is “current” from a setting you control — either where your cursor sits, or where the window already lives. When windows keep landing on the wrong screen, that setting is nearly always the mismatch. Change it in Rectangle’s preferences, and lean on the next/previous display shortcuts to move windows deliberately rather than hoping the guess lands right.
Why this happens in the first place
On one screen, “snap this window left” leaves nothing to interpret. Add a second display and the same command becomes a question: the left half of which screen? Rectangle has to choose, and it chooses by a rule you define.
There are two possible rules, both sensible. One treats the active display as wherever your mouse cursor currently is. The other treats it as wherever the window being moved already sits. Which one feels right depends entirely on how you work — which is precisely why it’s a setting instead of fixed behavior.
Virtually every “wrong monitor” complaint comes back to that rule clashing with the user’s mental model. Your hand does one thing, the app assumes another, and the window turns up somewhere you didn’t intend.
The fix: change which display counts as current
Open the Rectangle app‘s settings from the menu bar and locate the option governing how the current screen is decided — the choice between following the cursor and following the window.
Windows keep snapping to whichever display your mouse is on, when you wanted them to stay put? Switch to the window-based option. This fits people who fire keyboard shortcuts while the cursor idles elsewhere.
Windows keep staying on their own display, when you wanted them to follow your attention? Switch to the cursor-based option. This fits people whose mouse leads and who expect the window to come to where they’re looking.
Change it, then test with a window on each display. One of the two will match your instincts, and once it does, the problem usually vanishes permanently.
Move windows between displays on purpose
Guessing rules are fine; explicit commands are better. Rectangle includes dedicated shortcuts for throwing a window to the next or previous display, and using them kills the ambiguity outright.
Next display — Ctrl + Option + Cmd + →
Previous display — Ctrl + Option + Cmd + ←
The habit worth forming: move the window to the display you want first, then snap it into position there. Two keystrokes rather than one, but you get exactly what you meant every time, with no reliance on where the cursor happens to be sitting.
The clamshell problem
Running a MacBook closed with an external display attached — clamshell mode — produces its own variant of this. Lid shut, the built-in screen switches off and everything should land on the external monitor. Usually it does.
Things get strange around the transition. Close the lid while windows are still parked on the built-in display and macOS has to relocate them, which doesn’t always leave them where you’d expect. Rectangle then operates on whatever arrangement macOS produced.
The practical move is letting things settle before troubleshooting. After closing the lid or waking the machine, give macOS a moment to finish shuffling, then use the next/previous display shortcuts to place windows deliberately. If positions look clearly scrambled after a clamshell transition, quitting and relaunching Rectangle re-reads the current display setup cleanly.
After connecting or disconnecting a display
The same logic covers plugging in a monitor mid-session. Screen geometry shifts, and a running app can be operating from a stale picture of your displays.
If snapping turns odd immediately after you connect or disconnect a screen, quit Rectangle from the menu bar and relaunch. Five seconds, and it clears most transient multi-monitor weirdness. Try this before assuming a setting is wrong — especially if the identical setup behaved fine an hour ago.
Mixed resolutions and scaling
A laptop screen beside a 4K external at different scaling factors is the most common real-world arrangement, and it adds one more wrinkle: a window sized as “half” on one display is a different pixel count than “half” on the other. Move a window between them and it gets resized to match the new screen’s proportions.
That’s correct behavior rather than a fault, but it catches out people expecting exact dimensions to survive the trip. If you need a specific pixel size preserved across displays, that’s what Rectangle Pro‘s custom sizes are for — the free version works in fractions of whatever screen the window currently occupies.
Quick reference
Windows go to the cursor’s screen when you wanted them to stay — Switch to the window-based current-screen setting.
Windows stay put when you wanted them to follow the cursor — Switch to the cursor-based setting.
You want certainty every time — Use the next/previous display shortcuts to move first, snap second.
Confusion right after connecting or disconnecting a display — Quit and relaunch Rectangle.
Odd behavior after closing the laptop lid — Let macOS finish rearranging, then reposition deliberately.
Windows resize when crossing displays — Expected with different resolutions or scaling.
Frequently asked questions
Whether you’re using Rectangle for Mac with a single display or multiple monitors, its settings give you full control. Download Rectangle free and see how much easier window management becomes.
Why does Rectangle snap windows to the wrong monitor?
Rectangle determines the “current” display using a setting that either follows your mouse cursor or follows the window’s existing position. If windows land on the wrong screen, that setting doesn’t match how you work. Switching it in Rectangle’s preferences resolves most cases.
How do I move a window to another monitor in Rectangle?
Use Ctrl + Option + Cmd + Right Arrow for the next display and Ctrl + Option + Cmd + Left Arrow for the previous one. Moving the window deliberately before snapping it removes any guesswork about which screen the app will choose.
Does Rectangle work properly in clamshell mode?
Yes, though the transition can be messy. Closing the lid forces macOS to relocate windows from the built-in screen, and the result isn’t always tidy. Let macOS finish rearranging, then use the display shortcuts to position windows. Relaunching Rectangle clears up lingering confusion.
Why do windows resize when I move them between displays?
Because Rectangle works in fractions of the screen, and a half on a 4K monitor is a different pixel size than a half on a laptop display. The window is resized to match its new screen’s proportions. If you need exact pixel dimensions preserved, that’s a Rectangle Pro custom-size feature.