By Joel Dare - Written September 118, 2025
In a recent email course I use ImageMagick to reduce an image from 1.8MB to 28K. I do that often enough that I wanted to reproduce those steps in this article.
Here’s the full command I run for most images.
magick sailboat.png -resize 800x -strip -quality 75 sailboat.jpg
This takes the original image, sailboat.png, resizes it to 800 pixels wide and saves it as a jpg with a quality of 75%. That reduces the image quality quite a bit but also makes it much, much smaller. Smaller means faster, cheaper, and less carbon. It’s especially useful for users on slower internet connections, such as those in rural areas.
Interlacing causes the image to display in several passes so a coarse version shows first and progressively sharpens as more data arrives. This will only be noticeable on very slow connections.
Add -interlace Plane to the command to create a progressive image.
Here’s the full command with all the options.
magick sailboat.png -resize 800x -strip -interlace Plane -quality 75 sailboat.jpg
A user asked, “why use the JPEG format and not WebP?”
I use JPEG for the broadest compatibility and for historical reasons. It might be okay to switch to WebP, at this point, but I haven’t made that switch myself yet.
We’re probably to the point where WebP is common enough. It looks like the last browsers got support around 2020.
If you prefer WebP, the following command will work:
magick sailboat.png -resize 800x -strip -quality 75 sailboat.webp
WebP images will be smaller than their JPEG counterparts. Keep in mind, however, that WebP doesn’t support progressive images. On a really slow connection, a larger progressive JPEG might still feel faster than a smaller WebP image.
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