Alpha Channel Fixer
App Store Connect rejected your screenshot with IMAGE_ALPHA_NOT_ALLOWED? Drop the PNG here. It gets flattened and re-encoded as a true RGB PNG (color type 2, no alpha channel), then the output header is verified before you download.
Drop PNGs here
or click to choose files. Batch supported. Output is always a color type 2 PNG.
Why this tool exists
App Store Connect rejects any PNG whose file format declares an alpha channel, even when every pixel is fully opaque. The trap: nearly every convenient export path writes RGBA. Figma and Sketch exports, iOS Simulator captures piped through editing tools, and the browser's own canvas.toBlob('image/png') all emit color type 6 (RGBA). An "alpha fixer" built on canvas export would hand you back a file ASC still rejects.
This tool doesn't use the canvas encoder for output. It builds the PNG itself: your image is composited onto an opaque background, the raw RGB pixels are compressed with the browser's native CompressionStream('deflate'), and the IHDR, IDAT, and IEND chunks are written by hand with color type 2, the PNG format's "truecolor without alpha". After encoding, the tool re-parses its own output and shows you the verified color type. What you download is what App Store Connect accepts.
Prefer the command line, or want to understand the error first? Read why App Store Connect rejected your screenshot.
FAQ
How does it remove the alpha channel?
The PNG is decoded in your browser, drawn onto an opaque canvas (transparent pixels flatten onto your chosen background color), and re-encoded by a custom PNG writer that emits color type 2: three bytes per pixel, no alpha at the file-format level.
How do I know the output will pass App Store Connect?
The tool verifies its own output: after encoding, it parses the resulting file's IHDR header and shows the color type it found. When you see "color type 2" on the result card, the alpha channel is provably gone.
Does flattening change how my screenshot looks?
If your PNG was already visually opaque (the common case), no: the pixels are identical, only the file format changes. If it had genuinely transparent areas, those are filled with the background color you pick above.
Which browsers work?
Any modern browser with the native CompressionStream API: Chrome and Edge 80+, Safari 16.4+, Firefox 113+.
Related
Fixing rejections is the boring half.
ScreenshotPunch generates App Store screenshots with editorial art direction, exported flat and correctly sized from the start. Coming soon.
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