rn-size-check

React Native Android builds get big quietly. The AAB file size doesn't tell you what users download, and the usual causes (R8 off, every icon font bundled, PNGs that should be WebP, native libraries for every CPU) are spread across many files.

Each cause lives in a different place: Gradle settings, the Hermes bundle, Metro image assets, native libraries. And the JS bundle is one opaque file, so you can't see which npm package made it big.

• Read the build as a zip and work out which files one phone would really receive from Google Play: one ABI, one screen density.
• Read only what each check needs: the manifest for app info, the bundle header for Hermes, class names for R8, ELF section tables for debug symbols.
• Rank fixes by MB saved, list the files involved, and count a file flagged by two checks only once.
• Read the source maps React Native already writes to split the Hermes bundle by npm package, and suggest lighter options for heavy ones.
• Added compare: two builds or two saved reports in, and out come the files, packages and problems that changed.
• Put the analysis engine in a shared package so the same code runs in the CLI and in the browser.
• Add JSON and Markdown output, exit codes, --budget and --max-growth so teams can use it in CI.

Published on npm with a web version anyone can use without installing, and 1,000+ downloads in the first two weeks. On one real production app it found fixes worth about a quarter of the download size.