PNG Alpha Channel & Halo Inspector
The problem: Transparent PNGs exported from white backgrounds often contain subtle dirty fringe halos that look terrible on dark themes.
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PNG Alpha Channel & Halo Inspector: the complete guide
The PNG Alpha Channel & Transparency Artifact Inspector evaluates transparent PNGs and WebPs for semi-transparent edge halos, dirty alpha noise, and unflattened drop shadows. Inspect graphics against black, white, and checkerboard backgrounds with live pixel-level alpha distribution metrics.
The Danger of Dirty Alpha Halos on Dark Themes
When graphics are cut out from white backgrounds in graphic editing tools, semi-transparent white pixels often remain around the edges (fringe artifacts). While invisible on white backgrounds, these fringe pixels create distracting white halos when the graphic is viewed on dark mode websites or dark mobile themes.
Pixel-Level Alpha Distribution and Quality Scoring
Our inspector scans every RGBA pixel quad in the image buffer using the Canvas 2D API. It distinguishes between clean 1-bit binary masks, smooth anti-aliased vector edges, and unwanted low-opacity noise, calculating an overall Cleanliness Score out of 100.
Step by step: how to use PNG Alpha Checker
- 1
Upload your transparent PNG or WebP graphic, or inspect the built-in demo vector.
- 2
Review the Cleanliness Score and Alpha Mask Assessment report.
- 3
Toggle between Black, White, and Grid backgrounds to inspect edge halos under dark mode contrast.
- 4
Check the Semi-Transparent Pixels percentage to evaluate edge feathering quality.
- 5
Use the diagnostics to clean up cutout masks in your photo editor before deployment.
Security & privacy
Zero server interaction. Uploaded PNG files are analyzed entirely within your browser tab via HTML5 Canvas.