How to get a photo under a size limit (100 KB, 50 KB, 20 KB)

A JPEG gets smaller in two ways. Lowering its quality throws away fine detail the eye barely notices at first; pushed too far, it produces blocky edges and smeared skin. Reducing its pixel dimensions keeps every remaining pixel clean but leaves fewer of them, so the picture holds less detail when zoomed.

For a small target, a smaller image at decent quality looks far better than a full-size image crushed to the lowest quality. That is how the FormatOS image compressor works in target-size mode: it first lowers quality, but never below a level that still looks like a photograph. If the target is still out of reach, it reduces the dimensions instead and tells you the new size.

We gave the compressor one image, five times, with a different target each time. The image was a 4032 × 3024 landscape (the pixel size of an iPhone photo), saved as a quality-90 JPEG of 850 KB. It was cropped from the macOS “Sonoma” desktop picture, so it is smoother than a typical snapshot.

Every target was met, and each result landed just under it. Down to 200 KB the photo kept its full resolution. From 100 KB down, quality alone could not get there, so the pixel count dropped. At 20 KB the result is 766 pixels wide: fine for an ID thumbnail on a form, not for printing.

A real phone photo usually starts larger than our test image, because fine textures and camera noise take more data to store. Expect it to need smaller dimensions sooner, often already at 200 KB. The order of events is the same.

1. Open Compress Image and drop your photo. It is processed in your browser; it is not uploaded.
2. Choose Target size, then a preset (20 KB to 1 MB) or type your own figure in KB. Pick one slightly under the portal's limit.
3. Set the output format to JPG unless the portal asks for something else. PNG cannot use the quality lever at all (see below).
4. Press Compress. If the dimensions had to change, the result says so, for example “This image is now 1533×1150 pixels”.
5. Open the downloaded file and look at it at full size before uploading. Check faces, small print and edges.

Many forms ask for both: for example 600 × 600 pixels and under 50 KB. Do it in this order:

1. Crop to the shape the form wants (square, 3:4, and so on). Resizing a rectangle into a square without cropping stretches the face.
2. Resize to the exact pixel dimensions.
3. Then use the target size in Compress Image. A 600 × 600 photo has so few pixels that 50 KB is usually reachable by lowering quality alone, so the dimensions you set in step 2 stay as they are. Check them in the result; if they changed, raise the target.

PNG is lossless: it has no quality setting, so the only way to make a PNG smaller is to give it fewer pixels. If the form accepts JPG, convert to JPG first; it is usually several times smaller for photographs. Screenshots of text and line drawings are the exception, since they stay sharper as PNG.

For a photographed or scanned document, turning it into a clean black-and-white scan often removes most of the data before you compress at all.

• It does not know any portal's rules. It hits the size you ask for; choosing that size is up to you.
• It never adds pixels. If your target is larger than the photo already is, check the result: at a generous target it keeps full resolution at a higher quality, and the file can come out larger than your original. In that case keep the original.
• The saved image carries no camera metadata: in our test, the EXIF block (camera model, date taken, and GPS location if the phone recorded it) was gone from every result. That is usually what you want for an upload, but keep your original if you need the date it was taken.