Alpha channel

An alpha channel is the part of an image file that stores each pixel’s transparency. App Store Connect says screenshots can’t include alpha channels or transparencies, and Google Play wants JPEG or 24-bit PNG without alpha.

PNG files declare their pixel format in the header: RGB (colour type 2) has no alpha; RGBA (colour type 6) does, even if every pixel is fully opaque.

  • RGB (no alpha) — accepted3 bytes
  • RGBA (with alpha) — rejected4 bytes
Bytes per pixel in uncompressed 8-bit images

Frequently asked questions

How do I know if my PNG has an alpha channel?

Our size checker reads the PNG header and scans the pixels; on a Mac, Preview’s export dialog shows an “Alpha” checkbox.

Does JPEG have an alpha channel?

No. JPEG can’t store transparency.

How do I remove it?

Use the free alpha channel remover, or export as JPEG.

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