Why 50 KB comes up
50 KB is a common limit for profile pictures and compact thumbnails.
What happens to quality
A small, simple photo can stay recognizable. A large photograph usually needs a resize as well as lower quality. PNG screenshots often cannot reach 50 KB.
Why some images cannot reach 50 KB without resizing
The tool lowers quality, then dimensions, then stops at a documented minimum. Switch a stubborn PNG to WebP if the destination allows it.
WebP is the default output on this page because it is often smaller than JPG and much smaller than a lossless PNG. You can switch the format if the destination requires JPG.