What a circle crop really is
Pictures are rectangles. A circle crop does not change that: it keeps a square part of your picture and makes everything outside the inscribed circle transparent. The file is still a rectangle, for example 800 by 800 pixels, but you only see the circle. The corners together make up about a fifth of the square (the exact share is one minus a quarter of pi, about 21.5 percent).
Because the box is square, the circle touches all four sides of it. A larger box shows more of the picture, a smaller box zooms in. Nothing is scaled: the file has exactly the pixels inside the box, so a bigger box gives a bigger file. Away from the smoothed edge, the pixels of an opaque picture come out unchanged: we compared them with Pillow, the Python imaging library, and found no difference. Pixels that were already partly see-through can shift in colour by a level or two, because the browser stores them with their colour already multiplied by their transparency.
Which formats keep the transparent corners
- PNG keeps them, with exact pixels. It is the safe choice and works everywhere.
- WebP keeps them and usually makes a smaller file. Current browsers and most apps open it, but some older programs and upload forms do not.
- AVIF keeps them too, with the smallest files, but is slower to make and less widely supported.
- JPG cannot be transparent. If a circle were saved as JPG the corners would turn into a solid colour, so the tool does not offer it for circles.
Where the file ends up matters. A site that shows the file as it is keeps the transparent corners and shows whatever is behind the picture. A site that converts uploads to JPG fills the corners with a solid colour, often white or black. If that is not what you want, put a background colour behind the picture first.
Profile pictures: circle or square?
Many sites and apps show a profile picture in a circle themselves. They cut a circle out of whatever you upload, often from a square or from the middle of the picture. For those, the right file is a square crop, not a circle: choose Rectangle and the 1:1 ratio, place the box, and save. A circle with transparent corners can end up with a coloured rim after the site's own cutting.
A circle with transparent corners is the right file when the picture is shown as it is: an avatar on your own website, a round badge in a document or a slide, a sticker, a logo on a coloured background, a chat avatar that does not cut its own circle. Check what the site asks for, because the size it wants differs from site to site.
If you want rounded corners instead of a full circle, choose Rounded and set the corner radius with the slider. At 50 percent of a square box it is a circle again.
Getting a good circle
The circle touches the four sides of the box, so everything in the corners of the box is cut away. Keep the part that matters well inside: leave room above the head, because a circle takes more off the top corners of a portrait than a square does. A face sits well a little above the centre of the circle, with the eyes near the upper third.
Use the largest box the picture allows when you want to keep as much as possible, and a smaller box to zoom in on a face in a group photo. A small box means fewer pixels, so start from a picture that is bigger than the size you need. The preview after cropping is the real file, so you can check the edge before you download, and Crop again keeps the box for another try.