Crop a photo to 16:9
16:9 is the shape of most screens and videos. This page opens on 1920 x 1080 and lists the other 16:9 sizes.
SnapCut crops and sizes the photo only. It does not check your face, expression or background.
Your photo never leaves this device. To check, open your browser's developer tools, choose Network, and crop a photo: no request carries it.
The Widescreen 16:9 view in the picker lists every 16:9 size in SnapCut: the plain 1920 x 1080 frame, the YouTube thumbnail at 1280 x 720 and at 3840 x 2160, and the YouTube channel banner at 2560 x 1440. Each is the same shape at a different number of pixels.
Pick 1920 x 1080 when you need a general widescreen image for a slide, a video frame or a desktop background and no site names a size. It is a plain size with no platform behind it, so no source is cited. The other sizes in the list come with the page they are based on.
Cropping to 16:9 is a matter of choosing which horizontal band of the picture stays. A portrait photo loses a lot, since less than half of its height remains. Zoom in for a tighter shot, and use the position sliders to move the band up or down.
If you need more pixels, start from a bigger photo. SnapCut cannot create detail that is not in the picture; when the part you chose is smaller than the output it warns you that the crop will be enlarged.