How to resize a window to an exact size on Mac

Why a Mac has no “set window size” box

On a Mac, a window’s size belongs to the app, and macOS gives you three ways to change it: drag an edge, send it full screen (or, with ⌥, zoom it) with the green button, or — on macOS 15 and later — tile it to part of the screen. All three are about fitting the window to the screen you have. None of them is about a number, so there’s nowhere to type 1920 and 1080.

Most of the time that’s fine. It stops being fine the moment the number matters: you’re recording a demo that has to be exactly 1080p, taking screenshots that should all match, checking how your site looks at a laptop’s width, or making sure an app’s window looks right at the size your users will see. Dragging gets you close, and close shows up as a black border in the video or one screenshot a few pixels wider than the rest.

Ways to set an exact size with what macOS gives you

AppleScript, from Script Editor. Open Script Editor (in Applications → Utilities), paste this, change the two numbers and click Run: tell application "System Events" to tell (first process whose frontmost is true) to set size of front window to {1280, 800}. Because Script Editor is in front while you run it, it resizes Script Editor’s own window the first time; to size another app, put process "Safari" (or that app’s name) in place of (first process whose frontmost is true). macOS asks you to allow Script Editor in Privacy & Security → Accessibility the first time, because changing another app’s window needs that permission.

The same line from Terminal. Put it after osascript -e with the script in single quotes, and you can run it from a shell or a script. Terminal is in front while it runs, so name the app you want sized, as above, rather than asking for the frontmost one. Terminal is then the app that needs Accessibility permission. Add set position of front window to {0, 25} in the same way to move the window as well as size it.

Apps that understand bounds. Some apps, including Safari and Finder, can be asked for a window’s position and size together: tell application "Safari" to set bounds of front window to {0, 25, 1280, 825}. The four numbers are the left, top, right and bottom edges, so the width is right minus left and the height is bottom minus top. Instead of Accessibility, macOS asks once whether Script Editor (or Terminal) may control that app, under Privacy & Security → Automation. It only works in apps that support it.

Measure, then drag. If close is good enough, press ⇧⌘4 and drag across the window: the numbers beside the crosshair are the width and height of what you’ve selected. Press Esc, drag the window’s corner, and measure again. It’s trial and error, but it needs nothing installed.

Testing a website at a certain size? Size the page, not the window

If what you care about is how a web page looks at 1280 or 390 wide, the browser has a better tool than a smaller window. Safari’s Responsive Design Mode (Develop → Enter Responsive Design Mode, ⌥⌘R) shows the page at the width and height you type, or at the size of a chosen iPhone or iPad. If you don’t see a Develop menu, turn on “Show features for web developers” in Safari Settings → Advanced.

Chrome’s device toolbar does the same: open Developer Tools (⌥⌘I), click the device icon at its top left, or press ⇧⌘M while Developer Tools is open, and type a width and height. Both set the size of the page itself, so the browser’s tabs and toolbars aren’t counted in it — which a resized window can’t give you.

Points, pixels and the title bar: why 1920 × 1080 may not be 1920 × 1080

Mac window sizes are in points, not pixels. On a Retina display, one point is drawn with two pixels each way at the default scaling. So a window set to 1920 × 1080 points covers 3840 × 2160 pixels of the screen, and a full-resolution screenshot or recording of it comes out that size. If you need a 1920 × 1080-pixel file from a Retina Mac, either size the window to 960 × 540 or scale the recording down when you export it. On a non-Retina external display, points and pixels are the same.

The size includes the title bar and toolbar. A window’s size is its whole frame, so a 1920 × 1080 window has a little less than 1080 points of content under its toolbar. For a recording of the whole window that’s what you want; for content at an exact size, use the browser tools above or make the window that much taller.

It has to fit on the screen. A 1920 × 1080 window needs a display at least that big in points. A 13-inch MacBook Air at its default scaling is smaller than that, and with the menu bar taking its share, 1280 × 800 is the safe choice there; or record on an external display. Apps can also set a minimum and maximum size for their windows, and no tool can size a window past them.

If you only need a window big, not exact, Option-click the green button or press Fn-Control-F on macOS 15 to fill the screen. To make that the plain click, maximize without going full screen.

How the shortcut works in MacFixes

The fix is called Window layouts, and setting a window’s size is one half of it. It offers 1280 × 800, 1440 × 900 and 1920 × 1080, plus a custom size of your own, and each one can have a shortcut. Bring the window you want to the front, press the shortcut, and it takes that size. Every app’s window works the same way, so you don’t write a script per app.

Like any app that moves other apps’ windows, it needs Accessibility permission, which macOS asks for once. The fix is free.

The other half saves where every window is and puts them all back with one shortcut — a recording setup with the app on one side and notes on the other, say. That has its own page: save and restore window layouts. For quick halves, thirds and corners rather than exact sizes, snap windows instead.

Getting ready to record or present? A pile of notifications in the corner is the other thing that ends up in the video: clear every notification at once and hide the files on your desktop first.

Permissions, and turning it off

More fixes macOS doesn’t give you

One of 47 fixes and 10 apps in MacFixes. Every fix · Every app · Something else your Mac won’t do? Request it.