The Complete Guide to Image Resizing

Resizing is the fix for the most common image problem: files that are larger than the space they occupy. Done well, it is invisible — the image looks identical and loads faster. Done badly, it produces blurry, distorted or enormous files.

Downscale, never upscale

Shrinking an image averages pixels together, which usually improves perceived sharpness. Enlarging an image invents pixels the source never had, producing blur. Rule one of resizing: if you need a larger image, go back to the source — do not upscale.

Dimensions by use case

Aspect ratio: lock it or crop it

Distortion happens when width and height are set independently. Keep the ratio locked unless you are deliberately changing the shape — and for shape changes, crop rather than stretch. The Image Cropper handles the "change the shape" job properly.

Retina and density

A 400px-wide avatar slot on a phone with a 2× display benefits from an 800px image. The general rule: size for the highest-density display your audience uses, then stop. Beyond 2×, the extra pixels cost bytes and buy almost nothing.

Resize to a target file size

Sometimes the constraint is not dimensions but bytes — a form that rejects files over 200 KB, or an email limit. The Image Resizer's "target size" mode solves exactly this: it finds dimensions and quality that fit the budget.