Why a PNG is hard to compress
PNG keeps every pixel exactly, so it has no quality to lower. A photo saved as PNG is often several times larger than the same photo as a JPG. To reach a size in KB, the tool saves it in a format that can be compressed.
| Format | Good for |
|---|---|
| JPG | Photos for forms, email and the web: accepted everywhere |
| WebP | Photos and graphics with transparency at a small size; not every form accepts it |
| PNG | Screenshots, logos and drawings with few colours, where every pixel must stay |
Transparent backgrounds
JPG has no transparency: transparent parts of the picture turn white. Choose WebP under “More options” to keep them.
Quality first, then pixels
A JPG or WebP file gets smaller in two ways: a lower quality, which drops fine detail the eye hardly sees, or fewer pixels. The tool lowers the quality first, only as far as the photo still looks good, and then makes the photo smaller. Tick “Keep the dimensions” when the size in pixels must stay; then only the quality goes down.
When the photo itself is the problem
Compression makes a photo lighter, not better: it cannot fix a blurry, dark or badly framed picture. If the photo is for a CV, a profile or an application and you have no good one, a professional headshot made from a few selfies gives you one.