Check Image Transparency

No. The entire analysis runs in your browser using the HTML5 canvas API. The file is read locally, never sent to a server.

It decodes your image, draws it onto a canvas, then walks every pixel’s alpha byte. Pixels with alpha 255 are fully opaque; alpha 0 is fully transparent; anything in between is semi-transparent.

PNG, WebP, GIF, and a handful of others. JPEG does not – every JPEG pixel is opaque by definition, so the tool will always report 100% opaque for JPEGs.

Not every PNG has transparency. If the image was flattened against a solid background before export, or saved without an alpha channel, every pixel will be alpha 255. The tool correctly reports it as opaque.

It is any pixel whose alpha is strictly between 0 and 255 – so semi-translucent. A soft drop shadow, anti-aliased edge, or foggy overlay all create partially transparent pixels.

Only the first frame. Canvas decodes animated GIF and WebP as a single still image, so the tool reports on that frame and ignores later ones.

The mean of every pixel’s alpha byte (0-255). A fully opaque image averages 255; a half-transparent overlay averages around 128; a fully invisible image averages 0.

The lowest alpha value found in the image. If it is 255, every pixel is fully opaque. If it is anything less than 255 the image has transparency somewhere – useful when you want a yes/no answer at a glance.

No hard limit, but images over 8000×8000 pixels trigger a warning because memory caps vary by browser. Typical photos scan in well under 100 ms.

After the page loads, yes. HTML, CSS, and JS are self-contained, so you can disconnect Wi-Fi and keep checking images.