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How to resize an image on Mac

The Preview app that comes with every Mac can resize one photo or many at once. Open the images, choose Tools → Adjust Size, and keep “Scale proportionally” on.

Updated October 22, 2026

Resize one image in Preview

  1. Open the image in Preview.
  2. Choose Tools → Adjust Size.
  3. Pick pixels (or percent) and enter the new width or height.
  4. Keep Scale proportionally on so the photo isn’t stretched.
  5. Make sure Resample image is on to change the pixel count, then click OK.

Resize many images at once

  1. Select all the images in Finder and open them together in Preview.
  2. In Preview’s sidebar, select all of them (Command-A).
  3. Choose Tools → Adjust Size, set the size, and click OK.

Preview saves over the originals. Copy the photos to a new folder first if you want to keep the full-size versions.

Steps from Apple’s Crop, resize, or rotate an image in Preview guide, checked October 22, 2026.

Need an exact size for a website or shop?

Our image resizer works in any browser, resizes up to 100 photos without touching the originals, and has presets for Etsy, eBay, Amazon and Shopify. Need a file under a KB limit instead? Use compress to a size. For the right pixel sizes, see the photo size cheat sheet.

Frequently asked questions

How do I resize several images at once on a Mac?

Open them together in one Preview window, select them all in the sidebar, then choose Tools → Adjust Size. The new size applies to every selected image.

How do I resize without stretching the photo?

In Preview’s Adjust Size window, keep “Scale proportionally” turned on. Then change only the width or the height, and the other updates to match.

Does resizing in Preview overwrite the original?

Yes, Preview saves the change to the same file. To keep the original, duplicate it first (File → Duplicate) or use File → Export to save a resized copy.

How do I make a photo smaller in KB, not just in pixels?

Fewer pixels usually means a smaller file, but to hit an exact limit like 100 KB, use a compress-to-size tool. BananaFast’s does it in your browser.

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