Why WebP, and why it is safe in an APK
WebP is typically 25–35% smaller than JPEG at the same visual quality, and often 50–80% smaller than PNG for photos and illustrations — while still supporting transparency. On the open web you might hesitate because of old browsers; inside an APK there is no such worry. The page is rendered by Android's WebView, which is Chromium, and Chromium has decoded WebP since long before the oldest Android version an app can target today.
What the compressor does, step by step
- Finds every
.png,.jpgand.jpegin the archive. - Decodes each one, scales it down if its longer side exceeds the maximum you chose (1920 px by default — wider than any phone screen's CSS width times its pixel ratio in practice), and encodes it as WebP at the quality you set. Transparency is preserved.
- Compares sizes and only keeps the new file if it is smaller. Tiny icons and already-optimised PNGs are often better left alone, and are.
- In WebP mode, rewrites every reference to a converted file — in HTML, CSS, JavaScript, JSON, SVG and manifest files — from
.png/.jpgto.webp. - Packs everything else unchanged into a new ZIP.
A file name is only renamed when every image sharing that name (say, icon.png in two folders) got smaller. That keeps the link rewriting safe without needing to understand your code's folder logic.
Choosing the settings
| Content | Quality | Max size |
|---|---|---|
| Photos, hero banners, product shots | 0.75–0.80 | 1920 |
| Illustrations, UI art, screenshots with text | 0.85–0.90 | 1920 or none |
| Game sprite sheets and texture atlases | 0.90 | none — atlases rely on exact pixel positions |
| Pixel art | use "Keep formats" | none — lossy encoding blurs hard edges |
What it cannot see
Image paths assembled at runtime — 'img/' + id + '.png' — are not literal file names, so they are not rewritten. If your code builds paths like that, use "Keep formats" mode, which re-encodes JPEGs and resizes images in place without renaming anything. Always open the result in the builder's preview before building.