White plate, still in this tab
A lot of catalogues do not want alpha. They want a subject on #FFFFFF, evenly lit, with no living-room wallpaper and no drop shadow from a bedroom lamp. Peel’s solid mode composites the mask over a colour you pick. White is preselected on this page because that is the rule Amazon, many Etsy categories and most print-on-demand panels actually enforce.
The fill is a destination-over composite on the canvas. It is not a second photograph of a paper sweep. If the mask eats a white product on a white table, you will get a bite out of the object — raise contrast in the source still, or shoot against a darker cloth and peel again. A network trained to find “the subject” will not invent a missing bottle cap.
Why not screenshot the checkerboard
The checker is a preview aid. A PNG of that pattern will fail a marketplace validator and look like a bug in a theme. Solid white (or a brand hex) is the file they asked for. Keep the original on disk; Peel does not keep it for you.
Colour plates
Brand kits sometimes want #F5F5F5, a cream, or a packed colour. Change the fill, download, done. Edges are still PNG. If you need a true studio sweep with a floor horizon, that is a set, not a saliency net — Peel will not fake a cyclorama. Dropping a second photograph behind the subject is photo backdrop, not this hex fill.
Catalogue-specific notes are on product photos. Portraits on a white plate are a different crop and lighting problem; see portraits. What a listing form does after upload — recode, reject alpha, JPEG on their CDN — is marketplace, not this control.