Uploading: PNG keeps edges clean
PNG is lossless, so it preserves sharp edges and exact colors. If your image is a logo, icon, or anything with hard edges — and especially if it has a transparent background — upload a PNG. The transparency is kept through the conversion.
Uploading: JPG works, with a caveat
JPG is lossy. Its compression adds faint blocky artifacts and slightly smears colors, which can show up as noise when you reduce to a small palette. It still converts fine — most photos are JPG — just expect to lean a little harder on cropping and contrast to clean it up.
Tip If you have both a PNG and a JPG of the same image, upload the PNG.
Exporting: always PNG
Pixel art is made of hard-edged blocks of flat color — exactly the kind of image JPG is worst at. Save your result as PNG. It keeps every pixel crisp and, unlike JPG, supports transparency for sprites and cutouts.
What about WEBP and GIF?
WEBP is a modern web format and converts cleanly, much like PNG. GIF works too, though animated GIFs are handled as a single frame for now. Whatever you upload, export PNG for the sharpest result.