How to Bulk Resize Images on Mac (4 Methods)

You have 200 product photos at 4000px wide and you need them at 1200px for the website. Or 300 conference headshots that need to be 500×500 for the attendee directory. Or a folder of Retina screenshots that need to be halved for documentation.

Resizing one image takes ten seconds. Resizing two hundred takes a workflow.

Method 1: Picmal (resize + convert in one step)

Picmal lets you set a max width or height during conversion, so resizing happens alongside any format change. One step instead of two.

1. Drag your images or folders into Picmal
2. Choose your output format (or keep the same format)
3. Set the max width or max height in the resize options
4. Click Convert

Images larger than your specified dimension get resized down. Images already smaller are left alone — they won’t get stretched up. Folder structure is preserved in the output.

Best for: Preparing images for web or email. Resizing and format conversion at the same time (e.g., resize to 1200px + convert to WebP). Processing entire folder hierarchies.

Method 2: Preview (free, no install)

Preview handles batch resizing, though the interface is a bit awkward for large batches.

1. Select all the images in Finder
2. Right-click → Open With → Preview
3. In Preview, press Cmd+A to select all images in the sidebar
4. Tools → Adjust Size
5. Enter the width you want (make sure “Scale proportionally” is checked)
6. File → Save All (or File → Export Selected Images for copies)

Watch out: If you use “Save All,” Preview overwrites the originals. If you want to keep the originals, use Export Selected Images to a different folder.

Limitation: Preview applies the exact same pixel size to every image. No “50% of original” or “max 1200px” option, which means a mixed bag of landscape and portrait photos will end up with mismatched effective resizes.

Method 3: Automator Quick Action

Create a right-click menu option that resizes any selected images.

1. Open Automator → New → Quick Action
2. Set “Workflow receives” to image files in Finder
3. Add action: Copy Finder Items (choose a destination folder — this preserves originals)
4. Add action: Scale Images → set the pixel width or “To Percentage”
5. Save with a name like “Resize to 1200px”

Now select images in Finder → right-click → Quick Actions → “Resize to 1200px.” Done. The resized copies go to your chosen destination.

Best for: A resize you do repeatedly. Once set up, it’s two clicks.

Method 4: Terminal with sips

sips is built into macOS. No installs needed.

Resize all images in a folder to 1200px wide:

for f in *.jpg *.png *.heic; do sips --resampleWidth 1200 "$f"; done

Resize to a maximum of 1200px on the longest side:

for f in *.jpg; do sips --resampleHeightWidthMax 1200 "$f"; done

--resampleHeightWidthMax is the useful one — it resizes the longest side to 1200px regardless of orientation, so landscape and portrait images both come out with sensible dimensions.

Warning: sips modifies files in place. Copy the folder first if you want to keep originals.

Which method to choose

FAQ

Does resizing reduce image quality?

Resizing down has no visible quality impact. You’re discarding pixels the display wouldn’t have used anyway, and the resampling algorithm (usually Lanczos) produces clean results. Resizing up always degrades quality because the software is inventing pixels that weren’t there.

What width should I use for web images?

For most websites, the content area is 800-1200px wide. For retina displays, double that: 1600-2400px. A safe default is 1600px wide — it looks sharp on retina screens and is a reasonable file size. Hero images might go to 2400px; thumbnails can be 400-600px.

Can I resize images to exact dimensions (crop to fit)?

Resizing preserves aspect ratio by default — a 4:3 image stays 4:3. If you need exact dimensions like 500×500, that requires cropping, not just resizing. Preview can crop manually (Tools → Crop), but for batch crop-to-fit, you’ll need a more specialized tool.

How much does resizing reduce file size?

Roughly proportional to the pixel reduction. Halving the width and height (e.g., 4000×3000 → 2000×1500) reduces pixel count by 75%, and file size drops similarly. A 4000px wide JPEG at 8MB → 1600px wide at ~1.2MB is typical.