What makes a photo file large
The size of a photo file depends on two things: how many pixels it has and how much fine detail is kept in them. A photo straight from a phone camera often weighs several megabytes, while most forms and emails need a few hundred kilobytes at most.
| Limit | The tool keeps the file under |
|---|---|
| 20 KB | 20,000 bytes |
| 100 KB | 100,000 bytes |
| 500 KB | 500,000 bytes |
| 1 MB | 1,000,000 bytes |
A maximum or a minimum
Most sites set a maximum, for example “up to 200 KB”. Some also refuse files that are too small. Switch to “At least” and the tool makes the file larger instead: it raises the quality and, only if that is not enough, the size in pixels.
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.