- Drag it in, choose it, or paste it. It is read here in the tab and never uploaded.
- The settings column holds 4 controls for this tool. The defaults suit most files.
- “Optimize images” works on your device, then Original and Result sit side by side with a download.
About Optimize image
Optimize image makes a picture smaller in both ways at once: it scales the longest edge down to the length you need, then re-encodes what is left at the quality you set.
Most oversized images are oversized in two ways at once: too many pixels for where they are going, and encoded more generously than anyone will notice. This tool does both — scales the longest edge down to the length you pick, then re-encodes what is left at the quality you set.
The edge lengths are named after their use, because that is how the decision is actually made. 1920 px is a full screen, 1280 px is a picture on a web page, 800 px is a thumbnail. A four-thousand-pixel photograph on a page that shows it eight hundred pixels wide is costing everyone who loads it for nothing.
It never scales up: asking for an edge longer than the picture has leaves it alone rather than inventing pixels. For that, use Upscale image, which is built for it.
A size limit is for the form or the site that turns away anything over a given size. The quality comes down first, in small steps from the one you set, because that costs the least to look at; only when even the lowest quality worth keeping is too large does the picture get smaller as well. The limits count in thousands of bytes, so a file under 200 KB is under it however the site counts.