CrackMacHow to disable part of a MacBook screen and keep using the rest
macOS has no built-in way to switch off part of a display. Changing the resolution doesn't help, because the picture is always scaled to fill the whole panel. To make a Mac treat a damaged strip as if it weren't there, you need an app that confines windows, the menu bar and the pointer to the rest of the screen. That's what CrackMac does, for damage along the left, right, top or bottom edge, or two edges at once.
First, check where the damage stops
Open the free screen test and look at solid white and solid black. What you see decides whether blocking it off will work:
| What you see | Can it be blocked off? |
|---|---|
| A black, striped or flickering strip along one edge | Yes. This is the most common pattern after a drop. |
| Damage along two edges, such as the left side and the bottom | Yes. Each edge is set on its own. |
| A cracked or dark corner | Yes. Block off the edge nearest the corner, as far as the damage reaches. More on cracked corners. |
| Vertical lines across part of the screen | Yes, if they sit to one side. Block from that edge to the last line. More on lines after a drop. |
| Half of the screen black | Yes, you keep the working half. More on a half-black screen. |
| A spot or crack in the middle | No. Nothing can move the middle of the screen out of the way. |
| The whole screen black or unreadable | No. Use a monitor instead. Here's how. |
Why the usual tricks fail
- Lower resolution: everything gets bigger, but it still fills the entire panel, dead part included. The same goes for custom resolutions.
- Underscan: the setting that shrinks the picture on a TV is never offered for the built-in screen.
- A black wallpaper strip: hides noise on the desktop, but windows, menus and the pointer still go there.
- Window-tiling apps: they tile to the full screen too, because macOS reports the whole panel as usable.
- Zoom in Accessibility settings: magnifies around the pointer, which isn't the same as a smaller usable area.
How to set it up
- Download the free CrackMac trial and open it. It lives in the menu bar.
- Allow it in System Settings, Privacy & Security, Accessibility. That's what lets it move windows and stop the pointer.
- Choose Calibrate. A yellow line appears along one edge. Press 1, 2, 3 or 4 to pick the left, bottom, right or top edge, or click where the damage ends.
- Move the line with the arrow keys until it sits just past the damage. Hold Shift to move it faster.
- Press Return to save. Repeat for a second edge if you need one.
It takes about a minute. The setting is stored as a share of the screen, so it still fits if you change the resolution later.
What changes after that
- Windows can't be moved or opened into the dead area, and zooming a window fills only the working part.
- The dead area is painted black, so flicker and noise disappear.
- The menu bar, including the Apple menu, is redrawn inside the working area. Control-Option-Command-M opens every menu of the current app as a searchable list.
- The pointer stops at the edge, so you don't lose it in the black.
- Control-Option-Command-W lists every open window, which replaces Mission Control when its thumbnails land on the damage.
- The Dock can be made smaller so it fits on the good part.
On the MacBook Air CrackMac was built for, with a band down the left side and one along the bottom, the working area is about 85% of the screen. It feels like a slightly smaller laptop, not a broken one.
If the damage runs along one edge, CrackMac can keep windows, menus and the pointer off it. There's a free 30-minute trial.
What it can't do
- Damage in the middle of the screen can't be excluded, and CrackMac doesn't claim to.
- Mission Control and native full screen always use the whole panel. CrackMac can turn full screen into a window that fills the working area instead.
- If a strip shows noise whatever is drawn on it, painting it black won't hide it. Windows still stay out of it.
Control-Option-Command-Escape turns everything off at once if you ever need the whole screen back.
Other options
BetterDisplay, a general display utility, can also work around edge damage by streaming a smaller virtual screen onto the panel. Here's how the two compare. An external monitor avoids the problem entirely, and a repair fixes it. Both are compared, with prices, in cracked MacBook screen: your options.
Quick answers
Is there a macOS setting to use only part of the screen?
No. macOS always draws across the whole built-in panel, whatever resolution you choose. Keeping windows off one area needs a separate app.
Does lowering the resolution avoid a broken part of a MacBook screen?
No. A lower resolution makes everything larger, but macOS still stretches the picture across the entire panel, so the damaged area stays in use.
Can I use only half of my MacBook screen?
Yes, if the working half is on one side. Block off the broken side from the edge up to where the picture is clean, and windows, menus and the pointer stay on the other half. If the damage is in the middle of the screen, it can't be blocked off this way.
Does blocking off the broken part stop the crack from spreading?
No. It only changes what the Mac draws. To slow a crack down, open the lid by the middle of the edge, keep pressure off it, and carry the MacBook in a padded sleeve.
Does it affect an external monitor?
No. Each display is set up separately, so a monitor you plug in keeps its whole screen.
Damage along an edge?
CrackMac keeps windows, the menu bar and the pointer on the part of the screen that still works, and paints the dead strip black. You draw the line once, on a picture of your screen, and it stays out of your way after that.
- Works on macOS 13 or later, Apple silicon and Intel.
- Free for 30 minutes of use, then a one-time price. No subscription.
- A refund within 7 days, no questions asked.