Reduce iOS App Size and Boost Downloads: A Developer’s Guide 🚀

When users scroll through the App Store, they often make split-second decisions on whether to download your app. Surprisingly, one of the factors that influences that decision is app size.

Let’s break down practical ways to slim down your app without sacrificing features.

1. Optimize Image Assets

Images often take up the most space in an app bundle.

• Use SF Symbols where possible instead of PNGs.
• Replace large PNG/JPEGs with vector-based PDFs or SVGs (via third-party libraries).
• Enable Asset Catalog compression (.xcassets) to let Xcode optimize images for different devices.
• Adopt WebP or HEIF formats for high-quality, smaller images.

👉 Pro Tip: Audit your assets — many apps have unused images still shipping in production builds.

2. Use On-Demand Resources

iOS supports On-Demand Resources (ODR) — assets that are downloaded only when needed. For example:

• Download game levels on demand.
• Fetch large tutorial videos only when the user accesses them.

This keeps your initial app size smaller, making downloads faster.

let tag = "Level1Assets"
let request = NSBundleResourceRequest(tags: [tag])
request.beginAccessingResources { error in
    if error == nil {
        // Assets ready to use
    }
}

3. Optimize Code

• Bitcode (Optional Now): While Apple deprecated Bitcode submissions, smaller builds during development are still useful.
• Remove unused frameworks. For example, don’t bundle an entire ML framework if you’re using only one small model.
• Enable dead code stripping in Xcode (Other Linker Flags -> -dead_strip).

4. Compress and Split Binaries

• Use App Thinning: Apple automatically slices apps so devices download only the resources they need.
• Use Dynamic Frameworks wisely: Too many frameworks increase launch time and size. If possible, merge smaller modules.
• Apply LTO (Link Time Optimization) in Swift to reduce binary size.

5. Externalize Heavy Content

• Host large JSON, videos, or documents on a CDN instead of bundling them.
• Download ML models dynamically using Core ML model updates.
• Keep your app lean at launch — let the cloud do the heavy lifting.

✅ I’ve been through 80+ iOS interviews over the last few years — from startups to FAANG companies and I started noticing patterns in the questions, That’s why I created something I wish I had when I started: Cracking the iOS Interview — Cheat Sheet ♥

This Cheat Sheet can definitely 2X your chances of cracking your next big opportunity! Tried and tested by 200+ Devs.

6. Monitor and Test App Size

Before release:

• Check App Size Report in Xcode Organizer.
• Compare compressed size (download) vs installed size (after unpacking).
• Track how much space your app uses over time after updates — bloat creeps in slowly.

Conclusion

Reducing iOS app size isn’t just a technical optimization — it’s a growth strategy. By cutting down on unnecessary assets, using on-demand resources, and leveraging app thinning, you not only improve performance but also boost downloads.

✅ I’ve been through 80+ iOS interviews over the last few years — from startups to FAANG to companies like DoorDash — and I started noticing patterns in the questions, That’s why I created something I wish I had when I started: Cracking the iOS Interview — Cheat Sheet ♥

This Cheat Sheet can definitely 2X your chances of cracking your next big opportunity! Tried and tested by 200+ Devs.