What the checker looks at
It applies the same rules the builder applies when you convert a ZIP to an APK, so you find problems before a build rather than after an install:
- Start page —
index.htmlat the root, or one wrapping folder the builder strips, or (as a last resort) the shallowest HTML file. - Size — the zipped size of the files that will be kept, against 5 MB (free) and 18 MB (Pro), and an estimate of the final APK.
- Links — every
src,href, CSSurl()and@importin your HTML and CSS, resolved the way the app resolves them: root-relative paths, capitalisation mismatches, missing files, localhost URLs and external hosts. - Stowaways — source maps,
node_modules,.git, large videos and OS litter.
Is my ZIP uploaded?
No. The file is read with the browser's File API and decompressed with the built-in DecompressionStream. Close the tab and it is gone. That also means it works offline once the page has loaded.
After the check
Fix anything red, rebuild the ZIP, and check again. Then follow ZIP to APK to build it, or read the full ZIP preparation checklist.
Questions people ask
Why does the checker say a link is case-mismatched when it works on my computer?
Windows and macOS file systems ignore case, so Logo.png and logo.png are the same file there. Inside an APK they are different, and the link 404s.
Why are root-relative paths a problem?
The app serves your files from https://appassets.androidplatform.net/web/. A path starting with / points at the origin's root, outside /web/, so the file is not found.
Does it check JavaScript files?
It checks links in HTML and CSS. Paths built inside JavaScript at runtime are not visible to a static check — test those in the app or with the local /web/ reproduction.