Images are why bundled apps are big
When you make an app from an HTML file or a ZIP, everything in it ships inside the APK. Text — HTML, CSS, JavaScript — compresses to about a quarter of its size and rarely matters. Images are already compressed and go in at full weight, so a site with a few dozen photos is a 15 MB app with 200 KB of code in it. They are also what runs into the upload limit: 5 MB of source content on the free tier, 18 MB with Pro.
WebP is the fix. It is supported by every Android version that can run a website app, and it typically produces files 60–80% smaller than JPEG or PNG at the same visible quality. Converting the images is usually the single biggest size saving available, and it needs no change to your HTML beyond the file extension.
Quality and maximum width
Quality at 80 is the sweet spot — visually indistinguishable from the original for photos, at a fraction of the size. Go lower for backgrounds and thumbnails, higher only for images people will pinch-zoom. Maximum width resizes images that are larger than they will ever be displayed: a 4000-pixel photo shown 800 pixels wide is wasted bytes at any quality. 1920 covers full-screen imagery on any phone; 1280 covers large in-page images; 800 covers cards and thumbnails.
Drop a folder of images, set both, and download the ZIP. The table shows the original and converted size of each file so you can see where the saving came from.
When a file gets bigger
Small, flat graphics — simple icons, single-colour logos, screenshots of text — sometimes encode larger as WebP, because the format's overhead outweighs any saving on an image that was already tiny. The converter flags those; keep the PNG for them. Icons and logos usually belong in SVG anyway, which is text and compresses like it.
After converting, run the folder through the APK size calculator to confirm you are under the upload limit, then zip it and build. Or, if the site is image-heavy and changes often, make the app from its URL instead and let your server carry the images. Bundling in depth →