This image transparency checker walks every pixel of a decoded JPEG, PNG, or WebP and reports how the alpha channel is distributed. Alpha 0 is fully transparent. Alpha 1 through 254 is partially transparent. Alpha 255 is fully opaque. Has transparency is Yes when any pixel is below 255. Visible bounds are the inclusive rectangle of pixels whose alpha is above 0, with the origin at the top left. If no pixel has alpha above 0, the bounds are None.
The scan uses the bitmap the browser decoded. It does not open PNG private chunks, it does not parse a tRNS entry, and it does not read EXIF. A JPEG has no alpha channel, so the page says the decoded pixels are opaque even while it still prints the three counts. WebP and PNG can carry partial pixels. Those partial pixels are not rounded into opaque or clear.
One clicked sample is a different question. The Image Color Picker reports the alpha of the pixel under the pointer. This page answers whether any pixel in the whole image is transparent, and where the visible pixels start and end. If the result must stay transparent in a file, JPEG cannot hold it. The Image Format Converter is the export step, and the JPEG vs PNG vs WebP article already explains why alpha and JPEG disagree.
The preview sits on a light checker so a transparent edge is easier to see. The checker is page paint. It is not part of the count. Nothing is uploaded, stored, or requested from a remote image address.
A 2 by 2 PNG with one alpha 0 pixel, one alpha 128 pixel, one alpha 1 pixel, and one alpha 255 pixel reports 1 fully transparent, 2 partial, 1 opaque, Has transparency Yes, and bounds that skip the alpha 0 pixel. A PNG whose every alpha is 0 reports Has transparency Yes and bounds None. A JPEG of the same scene reports Has transparency No and a note that JPEG decode is opaque. A single pixel with alpha 10 is enough for Yes, and its bounds are that one coordinate.
The walk does not sample a thumbnail. A 16 megapixel image is counted in full or refused by the shared cap. There is no partial result when the file is too large.
Two browsers can disagree on a damaged WebP or on an orientation flag the decoder does not honor. The counts describe the pixels this browser produced. They are not a certificate that a file chunk is present. Use them before you flatten a logo to JPEG, and use the color picker when you need the alpha of one coordinate rather than the whole frame.
Every decoded pixel is counted. Alpha 0 is fully transparent, 1–254 is partial, and 255 is opaque. Visible bounds include any pixel with alpha above 0, origin at the top left. JPEG has no alpha channel after decode. This is not a PNG tRNS or EXIF read. SVG, GIF, and HEIC are refused. Limits: 8 MB, 8,000 px, 16 megapixels.
No. JPEG has no alpha channel. After decode every pixel is opaque, and the note on the page says so.
Yes. Any alpha from 1 to 254 is partial, and any alpha below 255 means the image has transparency.
Every pixel has alpha 0. There is no visible pixel, so the bounds are None.
No. Counts come from the decoded canvas. A tRNS chunk is not parsed, and EXIF is not read.
