How JPEG compression works
JPEG makes a photo smaller by simplifying fine detail the eye notices least. The quality setting decides how much: the lower it is, the smaller the file. In the middle of the range most photos look much the same on a screen at a fraction of the size.
| Quality | What happens |
|---|---|
| 92 | The highest this tool uses: above it, the file grows a lot for little gain |
| 60 to 92 | The range the tool works in: detail is simplified, the photo looks the same at normal size |
| Under 60 | Blocks and halos appear at edges, so the tool makes the photo smaller instead |
JPG or JPEG?
They are the same format. .jpg and .jpeg are two endings for the same kind of file, so a form that asks for JPEG accepts a JPG.
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.