How to Crop, Resize & Edit Photos on Mac

This guide walks you through cropping, resizing, and basic editing of photos on a Mac using the built-in Photos app and Preview. You’ll learn the exact steps to trim unwanted areas, change dimensions, adjust exposure and color, and save a copy without losing the original. No extra software is needed—everything here works with the tools already on your Mac.

What You’ll Need

• A Mac running macOS Ventura or later (the exact menu names may differ slightly on older versions).
• The Photos app (comes with macOS) or Preview (also built-in).
• The photo files you want to edit, either in your Photos library or saved on your Mac.

Step-by-Step

Crop a Photo in the Photos App

1. Open the Photos app and double-click the photo you want to edit.
2. Click the Edit button in the top-right corner (it looks like a slider icon).
3. Click the Crop icon in the toolbar (a square with corner brackets). The crop grid will appear over your photo.
4. Drag the corners or edges of the grid to select the area you want to keep. The parts outside the grid will be dimmed.
5. To force a specific aspect ratio (like 4:5 or 16:9), click the Aspect Ratio button in the top-right of the crop panel and choose a preset. You can also click Custom to enter your own width and height.
6. When you’re happy with the crop, click Done in the bottom-right. The original photo is preserved—you can always revert later.

Resize a Photo in Preview

1. Find the photo in Finder, right-click it, and choose Open With > Preview.
2. In Preview, go to the menu bar and select Tools > Adjust Size.
3. In the dialog that appears, you’ll see the current dimensions in pixels. You can change the width or height, and the other will adjust automatically if Scale proportionally is checked (it is by default).
4. Choose the unit you want—pixels, percent, inches, or centimeters—from the dropdown next to the dimensions.
5. Enter your new size, then click OK.
6. To save the resized version as a new file without touching the original, go to File > Export, choose a location, format, and quality, then click Save. If you just press Cmd+S, it will overwrite the original.

Basic Edits in the Photos App

1. Open the photo in Photos and click Edit.
2. Use the adjustment buttons on the right: Light (exposure, highlights, shadows), Color (saturation, warmth), and Sharpness.
3. Click the Auto button (a magic wand icon) to let macOS adjust the photo automatically.
4. To fine-tune, click the disclosure triangle next to each category and drag the sliders. You can also click the numbers and type a value.
5. If you make a mistake, press Cmd+Z to undo, or click Revert to Original in the bottom-right to start over.
6. Click Done to save your changes.

Rotate and Straighten

1. In the Photos app edit view, click the Crop icon.
2. Use the Rotate button (a curved arrow) to turn the photo 90° counterclockwise each click.
3. To straighten a tilted horizon, drag the Straighten slider (the circular dial icon) left or right.
4. Click Done to apply.

Common Mistakes

• Overwriting the original: When resizing in Preview, it’s easy to hit Cmd+S and lose the high-resolution version. Always use Export to save a copy.
• Changing aspect ratio unintentionally: If you uncheck “Scale proportionallyâ€� in Preview and only change one dimension, the photo will look stretched or squashed.
• Cropping too tightly: Once you crop, the removed pixels are gone (unless you revert in Photos). Leave a little extra space if you think you might need it later.
• Forgetting to hit Done: In Photos, if you close the edit window without clicking Done, your changes aren’t saved.

Tips

• Use the Auto Enhance button in Photos as a quick fix before you manually adjust anything.
• For social media, resize to the platform’s recommended dimensions (e.g., 1080px wide for Instagram) to avoid quality loss.
• When exporting from Preview, choose JPEG for photos, PNG for graphics with text, and HEIC for smaller file sizes on Apple devices.
• In Photos, you can apply the same edit to multiple photos: after editing one, select others, then go to Image > Copy Adjustments and Paste Adjustments.
• To quickly see the before/after, hold down the Shift key while in Edit mode in Photos.

Troubleshooting

Photo won’t crop or edit in Photos: Make sure the photo is actually in your library, not just referenced from an external drive. If it’s a file from elsewhere, import it first (File > Import).

Resize option is greyed out in Preview: This happens if the file is a screenshot or a PDF. For PDFs, you can’t resize the page in the same way—use Tools > Adjust Size only works on image files. For a screenshot, convert it to JPEG/PNG first by opening it in Preview and using Export.

Exported image is still huge: Check the file format and quality setting in the Export dialog. JPEG at 100% quality can be large; try 80% for a smaller file.

Edits not saving: In Photos, if you see a yellow “Editedâ€� badge but the changes don’t stick, you may have run out of storage. Free up space or save a copy to your desktop.

Frequently Asked Questions

Q: Can I crop a photo without losing quality?
A: Cropping removes pixels, so the remaining image has a lower resolution. If you crop a large photo to a smaller area, it may look pixelated when zoomed in. To keep quality, start with the highest-resolution original you have.

Q: How do I resize a photo to a specific file size (KB)?
A: Preview doesn’t show file size directly. After resizing, use Export and adjust the quality slider—lower quality reduces file size. Check the resulting size in Finder; repeat until it’s under your target.

Q: Does editing in Photos degrade the original?
A: No. Photos uses non-destructive editing—your original is preserved, and changes are stored as metadata. You can revert at any time.

Q: How do I batch resize many photos at once?
A: Select multiple photos in Finder, right-click, and choose Open With > Preview. Then select all thumbnails in Preview’s sidebar, go to Tools > Adjust Size, and it will apply to all. Then use File > Export Selected Images.

Q: What’s the best format for sharing photos?
A: JPEG is universally compatible and good for photos. PNG is better for images with text or transparency. HEIC is efficient but may not be accepted by all websites or apps.

Q: Can I undo a crop after I’ve closed the edit window?
A: In Photos, yes—open the photo, click Edit, then click Revert to Original. In Preview, if you saved over the original, you cannot undo. That’s why exporting a copy is safer.

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