How to divide the screen on a Mac: where each app belongs

Dividing a Mac screen takes about four seconds once the method is known. Deciding what belongs in each half takes longer, and getting that decision wrong is why so many carefully arranged screens are back to a pile of overlapping windows by lunchtime.

macOS actually offers three different kinds of division, and they are not alternatives to one another. One divides the desktop into regions. One divides the work into separate places. One divides across physical displays. Most frustration comes from using the first where the second was needed.

Three kinds of division

By region. Since macOS Sequoia 15, windows tile. Dragging a window to the left edge, the right edge or a corner snaps it into that region. Holding Option while dragging snaps faster. The green button offers layouts under Move and Resize for one window and under Fill and Arrange for several, and the Window menu carries the same entries grouped as Halves, Quarters and Arrange. Keyboard shortcuts come with it: Fn-Control-Left Arrow and Fn-Control-Right Arrow for halves, Fn-Control-F to fill, Fn-Control-R to undo, and Fn-Control-Shift-Left Arrow to place two windows at once. The menu bar and Dock stay visible throughout, and a third window can still be brought forward on top.

By place. Split View, reached from the green button under Full Screen, then Left of Screen or Right of Screen, does something different. It creates a new desktop space containing exactly those two apps. The menu bar and Dock hide until the pointer reaches them, nothing else can be placed beside the pair, and returning to the rest of the desktop means leaving the space. Additional spaces work the same way and are switched with Control-Left Arrow and Control-Right Arrow, with Control-Up Arrow opening Mission Control to see all of them at once.

By display. A second screen divides the work physically, and macOS treats each display as its own territory. Tiling acts on the display a window is already on, so each screen is arranged independently.

On macOS Sonoma 14 and earlier only the second and third kinds exist, since window tiling arrived in Sequoia. That single fact explains why older guides present Split View as the whole answer.

Decide from the content, not from the grid

A screen divided into equal halves treats both sides as equally deserving, and they almost never are. Three properties of the content decide where it belongs.

The first is whether it is being read or being worked in. Reference material tolerates a narrow column, because scanning a document does not need much width. The thing being edited does not: a cramped editing window forces constant horizontal scrolling and causes toolbars to collapse into overflow menus, which costs a click on every action.

The second is whether it changes on its own. Chat, mail and dashboards update whether or not they are being looked at, and that motion is exactly what pulls attention away from work. Something that updates by itself does not belong beside something that requires concentration, no matter how convenient it feels to have it visible.

The third is minimum width. Many apps have a point below which their layout breaks: sidebars vanish, columns collapse, toolbars truncate. That number decides whether a region is usable at all, and it is why quarters rarely survive contact with a laptop display while working comfortably on an external monitor.

A region is the right size when the app inside it stops needing horizontal scrolling, not when the pixels divide evenly.

Which region suits which app

Region	Suits	Reason
Left half, or the larger share	The thing being written or edited	Needs the most width, holds attention longest, breaks first when cramped
Right half, or the smaller share	Reference material, documentation, a source document	Read rather than manipulated, survives a narrow column
Top or bottom half	A terminal, a log, a transcript	Text that scrolls vertically wastes width it will never use
A quarter	A monitoring view, a timer, a queue that only needs a glance	Too small for interaction, adequate for a status check
A separate space	A task with two apps of its own, nothing else	Isolation is the point, and interruptions cannot reach in
A separate display	Anything that updates on its own	Motion is out of the working field of view but still checkable
Nowhere on screen	Notifications from services that can wait	The cheapest layout decision available

The last row is the one that gets skipped. A screen is easier to divide once fewer things have a claim on it, and hiding the active app with Command-H or minimising with Command-M removes a window from the argument faster than any layout does.

A working division for a single laptop screen

On a built-in display there are effectively two viable divisions, and the choice between them is not about pixels.

Halves work when both apps are genuinely in use at the same moment: a document and its source, a form and the data being copied into it. Fn-Control-Shift-Left Arrow arranges the pair in one keystroke, and Fn-Control-R puts things back.

The other viable division is full width plus a fast switch. One app fills the screen, the second lives one Command-Tab away, and nothing is halved at all. This is the better arrangement whenever the second app is consulted rather than watched, because a glance costs one keystroke and full width costs nothing.

Quarters on a laptop are mostly a photograph rather than a working layout. They look impressive and leave four windows too narrow for their own toolbars.

Thirds are the one division macOS cannot produce. A two-thirds and one-third split is the natural shape for a main task plus reference, and it exists in no menu and on no key. It is the single most common legitimate reason to install a window tool, and free options such as Rectangle, which is free and open source and supports macOS 10.15 or later, cover it.

Making a division stick

A layout that has to be rebuilt every morning is not a layout. Three habits are what make one survive.

Keep the same app on the same side. The value of a fixed arrangement is that the eyes stop searching, and that only happens if the left side is always the same thing. Swapping sides for a single task undoes a week of muscle memory.

Undo deliberately rather than by dragging. Fn-Control-R returns a tiled window to the size it had before, which keeps the arrangement reproducible. Resizing by hand leaves windows at sizes that no shortcut will restore.

Decide what happens to the pair when a third app is needed. Tiled halves allow a third window on top, and closing it leaves the pair intact, which is the main practical advantage over Split View. A Split View has to be left and re-entered, so anything that interrupts often belongs outside it.

Dividing by place instead of by region

When a screen resists division, the usual reason is that too many things want to be on it. Dividing the day rather than the display solves that.

The pattern that holds up is a small fixed number of spaces with stable contents. The main task on the desktop. A two-app pair, as a Split View or as tiled halves in the next space along. Something reference-heavy full screen in the space after that. Control-Left Arrow and Control-Right Arrow move between them, and because the contents are stable, muscle memory takes over within a day.

Mission Control is also the quickest way to build a pair out of something already full screen. Press Control-Up Arrow, drag a window onto the thumbnail of the full screen app in the Spaces bar, then click the Split View thumbnail that appears. Dragging one app thumbnail onto another does the same thing.

The limit is arithmetic. Each extra space adds an animation and a moment of working out where things went. Three or four places with fixed roles are navigable. Eight are a filing system nobody maintains.

Two displays change the arithmetic

An external monitor makes region division work properly, because minimum widths stop mattering, and it introduces one setting that causes most of the complaints about it.

Under Desktop and Dock, then Mission Control, the option for displays to have separate spaces determines whether each screen keeps its own spaces and its own menu bar. Turned on, each display is independent, full screen affects one screen, and Split View stays on the screen it was created on. Turned off, a full screen or Split View arrangement takes over both displays at once, which is behind most reports that an external monitor has ruined an otherwise working setup.

Tiling acts per display, so a window has to be on a screen before it can be tiled there. Dragging it across and then pressing Fn-Control-Left Arrow is the sequence, in that order.

The division that works with two screens is usually not symmetrical. One screen carries the work, halved or full width. The other carries the things that update on their own, where movement is visible without being in the way.

The division that collapses by itself

One arrangement fails no matter how carefully it is built, and the cause is not the layout.

Both halves are web apps, and both live as tabs in one browser. A layout arranges windows, and a tab is not a window. Dragging a tab out into a second window makes it placeable, and the arrangement looks correct for about an hour, until that window has collected four more tabs and the half of the screen reserved for the calendar is showing something else entirely.

The stubborn version is two accounts in the same service. Both windows share one browser session, so signing in to the second account signs out of the first. No layout feature has anything to offer there.

The fix is to change what is being divided. When each service has its own window and its own session container, the left half of the screen holds the same service all day, a second account is a separate place rather than a sign-out, and the tiling shortcuts start behaving as intended because there is a named window to aim them at. The features page describes that structure, and the supported apps list settles whether the specific services involved are covered.

What to change first

Pick the one app that needs the most width and give it the larger share, then put the thing that updates on its own somewhere it can be checked rather than watched, which usually means another space or another screen. Try Fn-Control-Shift-Left Arrow for the pair and Fn-Control-R to undo. If the halves keep filling with the wrong thing because they are browser tabs, a browser that gives each service its own window, such as SpaceDeck, is what makes a division stay put.