Rectangle Windows Snapping to the Wrong Monitor: Solved 

By Ryan Hanson, creator of Rectangle · Tested on macOS 15.5 with Rectangle 0.96 on a MacBook plus external display · Updated July 2026

Short version: Rectangle decides which display is "current" based on a setting you can change — either where your cursor is, or where the window already sits. If windows keep snapping to the wrong screen, that setting is almost certainly the mismatch. Change it in Rectangle's preferences, and use the next/previous display shortcuts to move windows deliberately instead of hoping the guess is right.

Why this happens at all

On a single screen, "snap this window left" is unambiguous. Add a second display and the same command becomes a question: left half of which screen? Rectangle has to pick, and it picks using a rule you set.

The two possible rules are straightforward. One says the active display is wherever your mouse cursor currently is. The other says it's wherever the window being moved already lives. Both are reasonable, and which one feels correct depends entirely on how you work — which is exactly why it's a setting rather than a fixed behavior.

Almost every "wrong monitor" complaint traces back to that rule not matching the user's mental model. Your hand does one thing, the app assumes another, and the window lands somewhere unexpected.

The fix: change which display counts as current

Open Rectangle's settings from the menu bar and look for the option controlling how the current screen is determined — the choice between following the cursor and following the window.

If windows keep snapping to the display your mouse happens to be on, when you wanted them to stay put, switch to the window-based option. This suits people who use keyboard shortcuts while the cursor sits idle somewhere else.

If windows keep staying on their own display, when you wanted them to follow your attention, switch to the cursor-based option. This suits people whose mouse leads the way 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 generally disappears for good.

Move windows between displays on purpose

Guessing rules are fine, but explicit commands are better. Rectangle has dedicated shortcuts for throwing a window to the next or previous display, and using them removes ambiguity entirely.

Next display — Ctrl + Option + Cmd + Right Arrow

Previous display — Ctrl + Option + Cmd + Left Arrow

The habit worth building is moving the window to the display you want first, then snapping it into position there. Two keystrokes instead of one, but the result is exactly what you intended every time, with no dependence on where the cursor happens to be.

The clamshell problem

Working with a MacBook closed and an external display connected — clamshell mode — creates its own version of this. When the lid is shut, the built-in screen is disabled and everything should land on the external monitor. Usually it does.

Where it goes strange is around the transition. Close the lid while windows are still positioned on the built-in display, and macOS has to relocate them, which doesn't always leave them where you'd expect. Rectangle then works from whatever arrangement macOS produced.

The practical approach is to let things settle before troubleshooting. After closing the lid or waking the machine, give macOS a moment to finish rearranging, then use the next/previous display shortcuts to place windows deliberately. If positions are clearly confused after a clamshell transition, quitting and relaunching Rectangle re-reads the current display setup cleanly.

After connecting or disconnecting a display

The same principle applies to plugging in a monitor mid-session. Screen geometry changes, and a running app may be working from a stale picture of your displays.

If snapping behaves oddly right after you connect or disconnect a screen, quit Rectangle from the menu bar and relaunch it. It takes five seconds and resolves most transient multi-monitor weirdness. This is worth trying before assuming a setting is wrong, especially if the same setup worked fine an hour earlier.

Mixed resolutions and scaling

A laptop screen next to a 4K external at different scaling factors is the most common real-world setup, and it introduces one more wrinkle: a window sized as "half" on one display is a different pixel count than "half" on the other. Moving a window between them means it gets resized to match the new screen's proportions.

That's correct behavior, not a fault, but it surprises people expecting the window to keep its exact dimensions. If you want a specific pixel size preserved across displays, that's what Rectangle Pro's custom sizes exist for — the free version works in fractions of whatever screen the window is on.

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

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.

Written and tested by Ryan Hanson, creator of Rectangle, on macOS 15.5 with a MacBook and external display.