Why does the background change?
JPEG cannot store transparent pixels. A transparent PNG or WebP must be flattened against a solid background when it becomes a JPG. Selecting the fill explicitly prevents the result from depending on an unwanted default. For example, a logo with transparent corners can become a JPG with white corners for a white document.
Choose the fill before downloading
Add the source images and choose JPG in Format. For an image with detected transparency, open its background color control and choose a color or enter a six-digit hexadecimal value such as #FFFFFF. The top background setting supplies the default for unchanged rows. A custom row can use a different color. Click Download to prepare and save the JPG.
Why is a row’s background control unavailable?
A PNG file is not necessarily transparent. It can contain fully opaque pixels, including a painted white background. The tool checks image pixels and only offers the row fill control when transparency can be flattened into JPG. Choosing a new fill will not replace an existing opaque background or remove a subject from a photograph.
Inspect soft edges
Partially transparent pixels, such as anti-aliased logo edges and shadows, blend into the chosen background. A dark logo may look different on white than on charcoal. Click the thumbnail to inspect the prepared image before using it. JPG quality changes may also introduce artifacts around fine text or sharp edges; choosing higher quality cannot recreate detail already lost in the source.
When to keep PNG or WebP
Keep PNG or WebP if the image must sit over different backgrounds later. Once transparency has been flattened into JPG, converting that JPG back to PNG does not recover it. Preserve the transparent original separately. Existing transparency can be retained in PNG or WebP output, but simply selecting PNG does not make an opaque image transparent.