When a 30KB limit is common
Limits around 30 KB often appear on student ID and admission forms, membership cards and staff directories. The photo is shown small, so the site keeps uploads light. It is still enough room for a clear color photo of a face at a few hundred pixels wide.
Compared with 20 KB, a 30 KB file has half as much data again. That shows up as cleaner skin tones, smoother backgrounds and sharper hair edges. If the form allows 50 KB, use the 50 KB target instead and the photo will look better still.
How to get a photo under 30KB
Upload the photo and keep the 30 KB target selected. PNG uploads are saved as JPG by default, so the target works for them too. The tool tries quality levels until it finds the highest one under 30 KB, and only shrinks the dimensions if the lowest quality is still too big.
A head-and-shoulders photo of about 350 by 450 to 450 by 600 pixels usually fits at a good quality. If your original is a large phone photo, resize it to that range first so the bytes go into detail you can actually see.
Tips for a sharper 30KB photo
Use a plain, light background and even lighting. Shadows, patterns and sensor noise all add data. Crop out empty space above the head and at the sides. Don't enlarge a tiny photo to meet a pixel requirement, as upscaling adds blur without adding detail.
Drag the compare slider across the eyes and hairline. Those areas show compression first. If they look smeared, resize the photo a little smaller and compress again, rather than accepting a blurry face.