App Thinning
ELI5 - The Vibe Check
App Thinning is Apple slicing your app into exactly the pieces a specific device needs, instead of shipping one giant binary with every screen resolution's assets and every device architecture's code baked in. An iPhone downloads iPhone assets, an iPad downloads iPad assets, nobody downloads the other one. Your listed app size and the actual download size are two very different numbers because of this.
Real Talk
App Thinning is a set of Apple technologies, including App Slicing and On-Demand Resources, that reduce an app's download size by delivering only the executable code and resources relevant to the requesting device's architecture, screen resolution, and capabilities. The App Store generates and serves these device-specific variants automatically from a single uploaded build.
When You'll Hear This
"App Thinning is why our App Store listing says 200MB but most users only download 80MB." / "We moved rarely-used assets to On-Demand Resources to shrink the initial App Thinning download further."
Related Terms
App Bundle
An App Bundle (AAB) is Android's smarter app format that lets Google Play build optimized APKs for each device.
App Store Connect
App Store Connect is Apple's portal where you submit your app and wait nervously for their review team to approve it.
Bundle Size
How big your JavaScript file is after everything is smooshed together. Every npm package you install makes it bigger. That 'tiny' date library? 70KB.
ProGuard
ProGuard is Android's code shrinker that removes unused code, renames everything to single letters, and makes your APK smaller.