What is an alpha channel?
An alpha channel is the part of an image that stores transparency. Alongside the red, green, and blue color channels, the alpha channel records how opaque each pixel is, from fully solid to fully see-through. Formats like PNG and WebP support an alpha channel; JPG does not.
How it works with color
A normal color pixel has three values for red, green, and blue. Adding an alpha value makes it RGBA, where the alpha decides how much of the background shows through. An alpha of zero is invisible, and full alpha is completely solid.
Why it matters
The alpha channel is what lets a cutout subject or a logo blend onto any background. Without it, the image would always carry a solid rectangle of color behind the subject.
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Frequently Asked Questions
What does RGBA mean?
RGBA is red, green, blue, and alpha. The alpha value adds transparency on top of the three color values.
Which formats have an alpha channel?
PNG and WebP have a full alpha channel. GIF supports a single fully transparent color. JPG has no alpha channel at all.