Almost-maximise sits on Control + Option + A (⌃⌥A) and sizes a window to roughly nine tenths of the display, centred, with a visible margin around it. The margin is the point: it keeps the desktop reachable for drag-and-drop, leaves room for notifications, and makes the window easy to grab.
What the margin is for
A window filling every pixel of the display seems obviously correct until three small things stop working.
Drag-and-drop to the desktop. Pulling a file out of an app and onto the wallpaper is the fastest route to a temporary copy, and it needs somewhere to drop. A full-width window leaves nowhere, so the file goes to Downloads and gets forgotten there.
Grabbing the window. Title bars are thin and edges at the screen boundary are hard to hit with a trackpad. A margin gives the pointer somewhere to land when you want to move or resize by hand.
Seeing what is behind. A sliver of another window at the edge is a reminder that it exists. Full width hides it completely, which is how people end up with fourteen windows and no idea what is open.
The shortcut, and setting it up
Install the Rectangle app from the official Rectangle download page, or run brew install rectangle. Free, MIT-licensed, macOS 10.15 or later, and it asks for Accessibility access on first launch because moving another application’s windows is privileged.
⌃⌥A then sizes the front window to almost the full display. Pressing it repeatedly cycles through progressively smaller proportions on recent versions, so a single key finds a comfortable size without any configuration at all.
This is not the same as filling the display, which has its own command and its own uses. The difference between full screen, zoom and fill is worth understanding separately before deciding which belongs on which key.
The notification problem nobody names
Notification banners arrive at the top right of the display and sit above whatever is there. With a full-width window they land on top of the content, which on a browser means covering the tab bar and on an editor means covering whatever sits in that corner.
A margin moves the collision off the window entirely. The banner appears over desktop rather than over work, which sounds trivial until you count how often a banner lands on the exact control you were about to click.
This is the least discussed argument for an undersized window and the one people notice first once they try it, usually within a day of switching.
Custom sizes for windows that need them
Presets cover most work, and a few windows want specific dimensions instead. A browser at a fixed width for testing a responsive layout. A video call window sized so faces stay legible beside a document. A terminal at a known column count.
Two approaches work. Size the window once by hand and rely on the application to remember it, which works for apps that save their own frames and fails silently for the rest. Or define the proportion in the window manager and bind it to a key, which is consistent across restarts and independent of what any application chooses to remember.
The second approach is worth the ten minutes if a specific size recurs weekly. It is over-engineering if it does not, and most people are better served by cycling through the built-in proportions than by maintaining a set of custom bindings they will forget. Custom window sizes on macOS are configured in the settings pane rather than through any system preference.
Where a margin is the wrong choice
Small displays. On a 13-inch laptop the nine tenths that looks elegant on a 34-inch monitor costs vertical space that matters, and the margin stops earning its keep somewhere around 15 inches.
Presentations and video. Any content an audience sees should fill the display, margin included, and full screen exists precisely for that.
Reference material during focused work. A document you are reading closely does better centred at a readable width than stretched to almost-full, which is a different command for a different job. Setup notes for Apple silicon and Intel machines are on the Rectangle Mac site.
Frequently asked questions
Is almost-maximise a macOS feature?
No. The system offers full screen, zoom and tiling to edges, none of which produces a deliberately undersized centred window. The command comes from third-party software.
How large is almost-maximise exactly?
Around ninety per cent of the display in the default configuration, though repeated presses step through smaller proportions. Treat the number as approximate and adjust by eye — the useful property is the margin existing at all, not its precise width.
Does it work the same on an external monitor?
Yes, and it sizes against the display the window currently occupies rather than the main one. On a large monitor the leftover margin is generous enough to keep a second window partly visible behind it, which is often exactly what you want. A free window manager for macOS applies the same proportion to every connected screen.
