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Image Transparency Inspector

Inspect alpha groups and supported hidden PNG colour values, with light and dark background previews.

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How this works

The tool runs in this browser. Your file or text is not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.

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One image up to 64 MiB and 24 megapixels. PNG reads hidden RGB under alpha zero when present; animated and 16-bit PNG are refused. JPEG/WebP use canvas decoding.

    How to use Image Transparency Inspector

    1. Choose a supported still image within the inspection bounds.
    2. Read the clear, partly transparent and opaque pixel counts.
    3. For PNG, inspect the reported nonzero RGB values beneath alpha zero.
    4. Compare the background previews and review edge fringes in the intended design.

    Example: Image Transparency Inspector

    Compare a hidden-colour pixel on two backgrounds.

    You add
    A static two-by-one RGBA PNG: the first pixel has RGB 255,0,0 and alpha 0; the second has RGB 0,0,255 and alpha 255.
    You get
    The report counts one clear pixel and one opaque pixel, including one nonzero RGB value beneath alpha zero. In the white-background preview the first pixel is opaque white.

    Supported inputs and limits

    File sizeOne image up to 64 MiB
    Working pixels24 megapixels
    FormatsJPEG, PNG and WebP within decoder limits
    One JPEG, PNG or WebP up to 64 MiB, 24 megapixels and 10,000 pixels on either side. PNG inspection accepts bounded static supported colour types up to 8-bit depth; animation, 16-bit data and low-bit grayscale are refused. Expanded PNG scanlines are capped at 40 MB and checked against declared dimensions before RGBA decoding. PNG may retain hidden RGB under alpha zero; JPEG/WebP canvas decoding cannot reliably expose it. White and dark previews are limited to 600 pixels on the longest side. Edge fringes do not prove premultiplication defects.

    Where your input is processed

    This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.

    Check the intended background

    A soft edge can look different over white and a darker colour. Compare both previews and then view the original in the actual design. Alpha groups describe the decoded pixels; they do not establish how every editor or viewer will resample those pixels.

    Questions about Image Transparency Inspector

    Why can a transparent PNG contain colour?

    RGBA pixels have separate colour and alpha values. A fully transparent pixel can retain RGB values even though it contributes no visible colour in normal compositing.

    Can it expose the same hidden RGB in WebP?

    Other supported formats use canvas decoding here, which may discard colour beneath zero alpha. The report marks that hidden-colour measurement as unavailable rather than claiming a zero count.

    Does an edge fringe prove premultiplication is wrong?

    No. Background previews can reveal a fringe worth checking, but scaling, compression, source colours and decoder conversions can also affect an edge.

    Why is an animated PNG refused?

    The bounded inspection processes a still image. Refusing animation avoids silently analysing one frame while decoding an unrestricted collection of frames.

    Project manager: Tony Hines · Content updated 4 October 2026 · Report a problem

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