What "Transparent Background" Actually Means

You cut out a background, save the result, and somewhere along the way it turns into a solid white (or black) rectangle again. This isn't a bug hiding somewhere in whichever tool you used. It's almost always one of two things: the file format you saved to structurally cannot hold transparency, or the app you opened it in doesn't render the transparency it has.

The fourth channel

A digital image normally stores three numbers per pixel: red, green, and blue intensity. Formats that support transparency add a fourth number per pixel, the alpha channel, which controls opacity rather than color: 255 means fully visible, 0 means fully invisible, and values in between are partially see-through. "Transparent background" just means the pixels outside your subject have their alpha set to 0. It's not a special mode or a layer, it's literally one more number stored alongside the color at every pixel.

Why JPG specifically can never do this

JPG's compression format has no alpha channel defined at all, at any quality setting, in any app. It isn't a checkbox someone forgot to add. The format's compression works by transforming blocks of color data (technically, transforming brightness and color-difference channels), and the spec simply never allocated a slot for a fourth, per-pixel opacity value. So "save this transparent cutout as a JPG" is asking for something the container format cannot represent, not a settings problem you can work around. When you export a transparent image to JPG, something has to go in the transparent areas, and encoders fill it with a flat color, almost always white, because they need a fallback and white is the least visually jarring default.

Which formats actually support it

PNG: full alpha channel, 256 levels of transparency per pixel. The standard choice for cutouts.
WebP: full alpha channel support, at meaningfully smaller file sizes than PNG for the same image.
AVIF: also supports full alpha, and compresses even further than WebP in most cases.
GIF: supports transparency, but only as a single fully-transparent color with no partial values, no soft edges, which is why GIF cutouts often look jagged around hair or curves.
JPG, BMP (without an alpha extension), and most video formats: no alpha channel, ever. There's no version of the format that adds it.

When even a PNG shows up white

Sometimes the file genuinely has a working alpha channel and still displays as solid white or black somewhere. That's a rendering problem on the viewer's side, not the file's: older versions of Word and some email clients flatten a pasted image onto a white canvas the moment it's inserted, discarding the alpha data in the process. Some chat apps and file browsers generate a quick thumbnail preview that skips alpha compositing entirely and shows whatever the app treats as its default background color underneath. The PNG on disk is fine in both cases, the specific app just isn't showing you what's actually stored in it.

Working with it

Remove Background outputs a PNG with a real alpha channel. To move between the formats that actually preserve transparency, use PNG to WebP or WebP to PNG, both of which keep the alpha channel intact.

Related guide

PNG isn't the only format with real transparency support. See which image file types support transparency for how WebP, SVG, GIF, and AVIF compare.