How to Resize an Image to Exact Dimensions
Somebody has asked for an image at exactly 1200 by 630 pixels, your photo is 4032 by 3024, and those two shapes are not the same shape. That is the whole problem with resizing, and it is why pictures come out squashed. The Image Editor handles it by keeping the frame fixed while you move the picture inside it.
Three operations that get called resizing
Scaling changes the pixel dimensions and keeps the proportions, so a 4000 by 3000 photo becomes 400 by 300. Nothing is lost except detail. Cropping cuts part of the picture away to reach a different shape. Stretching forces the picture into a new shape without cropping, and it is the one that makes faces look wrong.
If you need an exact size that is not your photo's shape, you have to crop. There is no way around it: something has to leave the frame. The only question is what, and that is a decision worth making deliberately rather than letting a tool make it for you.
Why the frame should hold the shape
Dragging a crop box around a picture means fighting to keep the box the right proportions. It is easier the other way round: lock the frame to the aspect ratio you need, then drag and zoom the picture behind it until the right part is showing. The editor offers the common ratios - square, four by five, three by two, sixteen by nine and the vertical versions - and holds whichever you pick.
For platform-specific sizes there is a shortcut. The Social Media Image Resizer already knows the pixel dimensions each platform expects, so you choose the destination rather than looking the numbers up.
Never scale up
Enlarging an image cannot add detail that was never captured. A 400 pixel logo blown up to 1200 pixels is a 400 pixel logo with soft edges, and no amount of sharpening recovers it. If you need something bigger, you need a bigger original. This is the single most common cause of a picture that looks slightly wrong and nobody can say why.
Common questions
What size should a website image be?
Match it to the space it will occupy, then double it for high-density screens. An image shown 600 pixels wide should be about 1200 pixels wide in the file. Beyond that you are sending bytes nobody sees.
Does resizing reduce the file size?
Scaling down does, substantially, because there are genuinely fewer pixels. For a further reduction at the same dimensions, run it through the Bulk Image Compressor.
Which part of my photo should I keep?
Whatever carries the meaning. For a portrait, the face, with a little room above the head. For a product, the product and a margin of background. Decide first, then crop to it.
Is my photo uploaded to a server?
No. Everything happens in your browser, so nothing leaves your device.
Why does my image look blurry after resizing?
Almost always because it was enlarged, or because it was already small and has now been shown larger than its pixel count supports. Start again from the biggest original you have.
Need an image at an exact size?