Batch Resize Images on macOS via CLI (The Native Way)

#macos #terminal #sips

If you often need to resize dozens of images tucked away in various subdirectories.
While apps like Photoshop or Lightroom are powerful, they are overkill for a simple task: resizing all png files to a maximum of 200px.

Forget installing heavy dependencies like ImageMagick.
macOS comes with a built-in "secret weapon" called Sips (Scriptable Image Processing System).

The Scenario

You have a project structure like this:

/assets/products/category-a/item1.png
/assets/products/category-b/item2.png

You want to resize these to 200px (max side) and save them as _200px.png in the same folders, keeping the originals intact.

The One-Liner Solution

Open your terminal, navigate to your root folder, and run:

find . -name "*.png" -exec sh -c 'sips -Z 200 "$1" --out "${1%.png}_200px.png"' _ {} \;

Breaking Down the Command

To understand what's happening under the hood, let's look at the components:

Command Part	Purpose
`find .`	Searches the current directory and all subfolders.
`-name "*.png"`	Filters only the files ending with your specific suffix.
`sips -Z 200`	Resizes the image so the largest dimension is 200px (preserving aspect ratio).
`--out ...`	Specifies the output path so we don't overwrite the original.
`${1%.png}_200px.png`	A shell trick to strip the `.png` extension and append our new suffix.

Why Sips?

Sips is remarkably fast because it is optimized for the macOS file system and hardware.
Unlike other tools, it:

Respects Color Profiles: It uses Apple's ColorSync technology.
Zero Install: It has been part of macOS for decades.
Smart Scaling: Using the -Z flag ensures your images never look "stretched" as it maintains the original proportions.

Pro Tip: If you want to overwrite the original files instead of creating new ones, simply use:
find . -name "*.png" -exec sips -Z 200 {} \;

Summary

Next time you're preparing thumbnails for a gallery or optimizing assets for a website, don't reach for a GUI.
The power of the macOS CLI is right at your fingertips.