What alpha represents
An alpha channel stores how opaque each pixel is. Fully opaque pixels show the image color; fully transparent pixels reveal whatever is behind the image; intermediate values create soft edges and shadows.
PNG and WebP can preserve this channel. When preparing an icon or product cutout, preview it on both light and dark backgrounds because edge halos can be hard to spot against a single color.
Converting to a format without alpha
JPEG cannot represent transparent pixels. A converter has to composite them onto a solid background before saving; otherwise those pixels need an explicit fallback color.
The GZ WebP-to-JPG tool defaults to white and lets you select a background. Keep a transparent PNG or WebP master when the cutout will be placed over varying page colors.
Frequently asked questions
Can a JPG have a transparent background?
No. JPEG has no alpha channel; transparent areas must be filled with a color.