Often you don't need to shrink an image "in general" but down to a specific weight — for example, "photo under 200 KB" for a form or an avatar. Let's look at how to do that and why it matters to tell file size apart from resolution.
File size and resolution are different things
- Resolution is measured in pixels (1920×1080) — it's "how many dots" make up the image.
- File size is measured in kilobytes (KB) or megabytes (MB) — it's "how much space" the file takes up.
You can reduce file size without touching resolution (through compression), or you can reduce the resolution instead. For a significant reduction in file size, you usually need both.
Two levers for reducing file size
1. Lower the resolution. If an image is huge but you only need it for the web, shrink its pixel dimensions with image resize. File size drops roughly in proportion to the area: halving a side roughly quarters the area — and the file size along with it.
2. Compress harder. In the image converter, turn on compression and lower the quality. For JPG and WebP, a quality of 60–80% gives a serious saving with almost no visible difference.
How to hit a target number of KB
Most tools don't let you simply type in "200 KB" — file size depends on the image's content. So work iteratively:
- Reduce the resolution to something reasonable (for the web, 1200–1600 px on the longer side).
- Compress with a quality of around 75%.
- Check the resulting size. Too big — lower the quality in steps of 10%.
Two or three tries and you'll land in the range you need.
Which format to choose
- JPG — for photos, the smallest file size.
- PNG — for screenshots and graphics with sharp edges, but heavier.
- WebP — the lightest at the same quality, if compatibility isn't a concern.
If you have a heavy PNG photo, converting it to JPG alone will shrink the file size several times over. Processing happens on the server, and the file is deleted right away.