Source: https://mactoolbox.app/glossary/alpha-channel

# What is an alpha channel?

By Nikhil Barik · Published November 3, 2026

## Quick answer

An alpha channel is the part of an image that stores transparency. It lets areas of the picture be fully or partly see-through.

## What it is

Most images store red, green and blue for each pixel. An alpha channel adds a fourth value saying how opaque the pixel is.

## Why it matters on a Mac

Logos, cutouts and icons need transparency to sit on any background. JPEG has no alpha channel, so saving a cutout as JPEG fills the transparent area with a solid color.

## Which formats support it

PNG, TIFF, HEIC and WebP can store alpha. JPEG cannot. GIF supports only on-or-off transparency.

## How Toolbox handles it

Remove Background lifts the subject out of a photo and saves a PNG, with a transparent, white or custom color background, using Apple's Vision framework on your Mac. Convert Images can write PNG, TIFF, HEIC or WebP.

## Frequently asked questions

**Why did my transparent background turn white or black?**

The format you saved as probably has no alpha channel, such as JPEG.

**Which format is best for transparency?**

PNG is the most widely supported.

**Does Remove Background work offline?**

Yes. It runs on your Mac.

## Tools mentioned

- [**Remove Background**: Lift the subject out of photos and save it with a transparent or solid background.](https://mactoolbox.app/remove-background-from-image-mac)
- [**Convert Images**: Save photos as JPEG, PNG, HEIC, TIFF or WebP.](https://mactoolbox.app/heic-to-jpg-mac)

## Keep reading

- [Remove Background](https://mactoolbox.app/remove-background-from-image-mac)
- [Convert Images](https://mactoolbox.app/heic-to-jpg-mac)
- [PNG](https://mactoolbox.app/glossary/png)