Free Alpha channel inspector
Inspect PNG and WebP Alpha values, measure transparent coverage, and reveal edge problems against three preview backgrounds.
PNG, WebP, or JPG up to 10 MB. The image stays on this device.
File format vs pixel data
PNG is a container that can preserve an Alpha channel, but many PNG files are fully opaque. Export tools can flatten artwork against a white, black, or colored background while keeping the .png extension.
This checker reads actual pixel Alpha values from a browser-local Canvas. If every sampled pixel has a value of 255, the image is effectively opaque even if its filename suggests otherwise.
Edge quality
Anti-aliasing, shadows, glow, hair, glass, and soft masks use partially transparent pixels. These edges can look correct on a checkerboard but reveal pale or dark halos when placed on a different surface.
Switch between the light and dark previews before publishing. If an edge only looks clean on one background, return to the source mask and remove leftover matte color.
Three possible results
No sampled pixel has Alpha below 255.
Pixels are either fully visible or completely transparent.
Some pixels contain partial Alpha for softer transitions.
Alpha channel basics
The browser draws a scaled version of the image to a local Canvas and reads the Alpha value of sampled pixels. The file is not required to be uploaded.
Yes. PNG supports transparency, but a particular PNG can still contain only fully opaque pixels. The file extension alone does not prove that Alpha information is present.
Binary transparency uses fully visible or fully invisible pixels. Smooth transparency also includes partial Alpha values, which are common around soft edges, shadows, hair, and glow.
Edge halos and leftover background pixels can disappear on one surface and become obvious on another. Testing both makes mask problems easier to spot.
No. Standard JPEG does not support an Alpha channel. If you need transparency, create the mask and export the finished image as PNG.
Alpha missing?