No crop photo in a 16:9 widescreen frame
Widescreen is 16:9, wider than it is tall. This page opens on 1920 x 1080 pixels.
Your photo never leaves this device. To check, open your browser's developer tools, choose Network, and export a photo: no request carries it.
Widescreen is 16:9, 1920 x 1080 pixels, the shape of most screens and video. It is the one frame here that is wider than it is tall, so a portrait photo becomes a narrow column with fill on both sides.
A 3:4 portrait photo is scaled to 810 pixels wide and 1080 tall, leaving 555 pixels of fill on each side. Blur turns those sides into a soft wash of the photo's own colours, which works well for a slide, a banner or a desktop background. For a plain look, pick White or Black.
A photo that is already 16:9 needs no padding, and a notice says it fits as it is. A photo that is only close, like 3:2, is 1620 pixels wide at full height and leaves 150 pixels of fill on each side.
Photos smaller than the frame are scaled up to fit, and a notice shows from what size to what size so you can judge whether it will look soft. Export saves a JPEG at a quality you choose, or a PNG, at exactly 1920 x 1080 pixels.