Save Mac screenshots as JPG instead of PNG

You took a screenshot of an article, your Desktop is full of 3 MB PNGs, and you’re wondering why a screenshot of mostly text needs to be so large. macOS defaults to PNG because it’s lossless — but for most screenshots that doesn’t matter, and JPG is often a quarter of the size.

Why this happens

PNG is the default for ⌘+Shift+3 and ⌘+Shift+4 because Apple wants pixel-perfect captures by default. For screenshots of UI, that often matters. For screenshots of webpages, photos, or anything photographic on screen, it doesn’t — JPG at quality 85 looks identical and is much smaller.

Change the default format

There’s no UI for this; it’s a defaults command in Terminal:

defaults write com.apple.screencapture type jpg
killall SystemUIServer

That tells macOS to save new screenshots as JPG. The killall restarts the UI service so the change takes effect. Other valid types:

• png (default)
• jpg
• pdf
• tiff
• bmp

To revert:

defaults write com.apple.screencapture type png
killall SystemUIServer

Quality control with the default JPG

macOS uses a fixed JPG quality (around 70–80) for screenshots. There’s no setting to change it. If you need higher or lower quality, take the screenshot as PNG and convert it afterwards.

Converting existing screenshots

Preview: open, File → Export, choose JPEG, set quality, save. Fine for one.

sips:

sips -s format jpeg -s formatOptions 85 screenshot.png --out screenshot.jpg

Folder:

for f in *.png; do
  sips -s format jpeg -s formatOptions 85 "$f" --out "${f%.png}.jpg"
done

The faster way

Drag a folder of PNG screenshots into Melt, set output to JPEG, pick quality, click Compress. Useful for cleaning up a Desktop full of accumulated screenshots. Download Melt.

Convert screenshots in Melt

1. Open Melt.
2. Drag your PNG screenshots in.
3. Set output to JPEG.
4. Quality 85 is a sensible default.
5. Click Compress.

When you should stay on PNG

• Screenshots of text where you’ll zoom in (PNG keeps text crisp; JPG can blur it).
• Screenshots with transparency (PNG supports it, JPG doesn’t).
• UI captures for design or development review.
• Anything destined for app store screenshots or marketing where quality really matters.

For everyday screenshots that you’re going to glance at and delete, JPG is the better default.

What you lose, what you keep

PNG → JPG is lossy. Sharp text and UI edges look slightly softer; high-contrast lines can show JPEG artefacts. For screenshots of photos, gradients, or general web content, the loss is invisible. The file-size savings are dramatic — typically 70–80% smaller. Set the default and keep PNG for the cases where it actually matters.