TIL: sips: macOS Hidden Image Swiss Knife | Kondasamy Jayaraman (Samy)

Today I discovered sips (Scriptable Image Processing System) has been shipping with macOS since Panther (10.3) and I’ve been opening Preview like a caveman this whole time.

I was copying research paper images into a blog post and needed to check dimensions, batch resize, and convert formats. Instead of opening each file in Preview, I ran one command and got instant results.

The Commands That Replaced My GUI Habit

# Check dimensions of all images
sips -g pixelWidth -g pixelHeight *.png

# Resize all PNGs to max 1200px (preserves aspect ratio)
sips -Z 1200 *.png

# Convert PNG to JPEG with quality 80
sips -s format jpeg -s formatOptions 80 image.png --out image.jpg

# Resize and output to a separate directory (originals untouched)
mkdir -p resized
sips -Z 1200 *.png --out resized/

# Rotate 90 degrees
sips -r 90 screenshot.png

# Flip horizontally
sips -f horizontal image.jpg

The -Z flag is the one I use most. It scales down to fit within a maximum pixel dimension while preserving aspect ratio. No math required.

Quick Reference

Flag	What It Does	Example
`-g key`	Get a property	`sips -g pixelWidth img.png`
`-Z maxSize`	Resize preserving ratio	`sips -Z 1200 *.png`
`-z h w`	Resize to exact dimensions	`sips -z 630 1200 img.png`
`-s format`	Convert format	`sips -s format jpeg img.png --out img.jpg`
`-r degrees`	Rotate	`sips -r 90 img.png`
`-f direction`	Flip	`sips -f horizontal img.png`
`-c h w`	Crop to dimensions	`sips -c 630 1200 img.png`
`--out`	Write to file/dir	`sips -Z 800 *.png --out small/`

Where I Use It Now

Blog image pipeline. Before committing images to my portfolio repo, I normalize everything to 1200px max width:

find public/images -type f -name "*.png" -print0 | \
  xargs -0 -I{} sips -Z 1200 "{}"

Quick format conversion. When a tool spits out WebP or TIFF and I need PNG:

sips -s format png screenshot.webp --out screenshot.png

Dimension checks. Before writing image markup, confirm the actual size:

sips -g pixelWidth -g pixelHeight public/images/og-*.png

What I Learned

sips ships with every Mac. Zero install, zero dependencies
-Z is the everyday workhorse: one flag, aspect-ratio-safe resizing
Without --out, sips modifies files in place. Add --out to preserve originals
Supports JPEG, PNG, TIFF, GIF, BMP, PSD, PDF, and WebP
For anything beyond resize/crop/convert (compositing, text overlays, filters), reach for ImageMagick instead
man sips on macOS has the full property and format list

Found a CLI tool hiding in plain sight on your machine? I’d love to hear about it. Reach out on LinkedIn.