Crop from the original, not the preview
The preview is scaled to fit your screen, but the selection is measured in the image’s own pixels. Crop a 4000 pixel photo to half its width and you get a 2000 pixel result, not a 450 pixel one.
That sounds obvious and plenty of online croppers get it wrong, handing back an image the size of the preview they showed you.
The ratios worth knowing
| Ratio | Where it belongs |
|---|---|
| 1 : 1 | profile pictures, avatars, product thumbnails |
| 1.91 : 1 | link previews on social platforms and in chat |
| 16 : 9 | video thumbnails, presentation slides |
| 9 : 16 | stories and vertical video |
| 4 : 5 | portrait posts, which take the most feed space |
| 4 : 3 | classic photo prints and many camera sensors |
Pick the ratio before you compose the crop. Framing a shot and then forcing it into a different ratio is how faces end up half out of frame.
Format and quality
JPEG for photographs, at 90 or above. PNG when you need transparency or a lossless result, at the cost of a much larger file for photographic content. WebP when the destination is the web and you control it, because it is meaningfully smaller than JPEG at the same visual quality.
A JPEG crop is re-encoded once. That is one generation of loss, which is invisible at 90. Cropping the same file repeatedly, each time re-encoding, is what visibly degrades an image.
A side effect worth knowing about
Cropping here redraws the image onto a canvas, and a canvas holds pixels and nothing else. Every metadata block, including GPS coordinates, is gone from the result.
That is convenient when you want it and surprising when you do not, so it is stated rather than left to be discovered. If you want to see what a photo was carrying first, the metadata tool reads it out before removing anything.
Questions
Does cropping lose quality?
The crop itself takes the original pixels untouched. Only the re-encoding costs anything, so choose PNG for a lossless result, or JPEG at 90 and above where the difference is invisible.
Why do the preview and the result differ in size?
They do not. The preview is scaled down to fit the page, but the selection is stored in original image pixels, so a crop of a 4000 px photo comes out at full resolution.
Which aspect ratio should I pick?
1:1 for profile pictures, 1.91:1 for link previews and social cards, 16:9 for video thumbnails, 4:5 for portrait posts. Free when you just want to remove something.
Can I crop on a phone?
Yes. The selection is drag and resize with touch as well as mouse.
Does this remove the photo's metadata?
Yes, as a side effect: the crop is redrawn onto a canvas, which keeps pixels and nothing else. Use the metadata tool if you want to see what was there first.