What Is Alpha Transparency?
A fourth value on every pixel that says how see-through it is — and the reason a logo sometimes arrives with a white rectangle around it.
Alpha is a fourth number attached to every pixel that says how opaque it is. Colour normally takes three: how much red, green and blue. Alpha adds a fourth — 0 means completely see-through, the maximum means completely solid, and everything between is partly there, like coloured glass.
“Transparency” is that channel doing its job. When a format has no alpha channel, it has nowhere to record “nothing here”, and that single missing number is behind almost every version of the white-box problem.
The checkerboard is not part of your image
Every image editor draws transparent areas as a grey checkerboard. It is a convention, not content — the checkerboard means “these pixels have alpha 0”, and it does not exist in the file. It is drawn so you can tell a transparent hole from a white one, because on a white page they look identical until the moment you put the image on something coloured.
Which formats keep it
PNG has alpha. WebP has alpha. SVG has it by nature — it only draws the shapes you asked for. JPG has none at all, and this is not an oversight: JPG was built for photographs, and photographs are rectangles with something in every pixel.
So when you convert a PNG to JPG, the transparency cannot come along. It has to become some colour, and that colour is white by default. Your logo does not gain a white box because the tool did something clumsy; the box is what transparency turns into when the destination has no way to say “nothing”.
Where this actually catches people
Cutting a subject out and saving the result as JPG is the classic. Remove Background produces a genuine cut-out with an alpha channel, and if you then save it as JPG you have flattened the hole straight back to a white rectangle — the work is undone in a format choice. Save it as PNG. Our guide on removing a background is blunt about this because it is the single most common way people lose a cut-out.
Round crops are the other one. Crop to Circle works by making the corners transparent — the image itself is still a rectangle, because all images are. Save that as JPG and the corners fill white, and your circular avatar arrives as a circle in a white square. The round-crop guide covers it.
The rule is short: if any part of the image needs to not be there, it has to stay in a format with an alpha channel.
Partly transparent is a real thing
Alpha is not a yes/no switch. Mid-range values are what make a cut-out look convincing rather than cut with scissors — the soft edge on a strand of hair is pixels that are partly the subject and partly nothing. It is also how a watermark can sit over a photo without hiding it. Formats that support only on/off transparency, like GIF, are why old cut-outs have that crunchy jagged fringe: with no in-between, every edge pixel has to pick a side.
FAQ
Why does my transparent PNG have a white background now?
Something along the way converted it to a format without alpha — most often JPG. Transparency has to become a colour when it is flattened, and white is the usual default. Go back to the PNG; the JPG cannot be repaired.
Does JPG support transparency at all?
No. Not at any quality setting, and not in any variant you will meet. If you need transparency, you need PNG or WebP.
Is the checkerboard saved into my file?
No. It is how editors draw “nothing here” so you can see it. The file stores an alpha value; the checkerboard is the interface, not the image.