How to Crop a Wallpaper in Preview on Mac
Preview can crop an image to keep the part you want and resize the result for your Mac. Start with a high-resolution original and work on a copy: cropping removes pixels outside your selection.
Before you crop
Find your display’s native width and height in its specifications or our size guide. Divide width by height to get its aspect ratio. For example, 3840 × 2160 is 16:9. Your source needs to be large enough after the crop, not just before it.
Crop a copy in Preview
- In Finder, select your image and choose File → Duplicate. Open the copy in Preview.
- Show the Markup toolbar and choose Rectangular Selection.
- Drag around the area you want to keep. For dimensions while selecting, choose Tools → Show Inspector and open the Crop Inspector.
- Adjust the selection to approximately match your screen’s proportions, then click Crop. Check that the subject has room around the edges.
- Save the copy and set it as your wallpaper. If it crops unexpectedly, revise the selection.
Resize without stretching
In Preview, choose Tools → Adjust Size and keep Scale proportionally selected. Reducing an oversized image can make the file easier to handle. Enlarging a small image adds pixels but cannot recover lost detail. A crop close to your display’s proportions will usually need less adjustment when you fill the screen.
See Apple’s Preview instructions for undo and resizing options. For a photo in the Photos app, its Crop tool also offers preset and custom aspect ratios.