Signs your app needs modernization
Old code isn't a problem by itself. It becomes one when it slows the business down or creates risk. These are the signals we see most often:
- Small features take weeks because every change breaks something else.
- The app is built on a framework that is no longer supported, such as Xamarin, or on plugins nobody maintains.
- Each new iOS or Android release causes a scramble of urgent fixes.
- You struggle to hire developers who know, or want to work in, the current stack.
- Store requirements, such as a new target API level or SDK, are hard or impossible to meet.
- Ratings mention slowness, crashes or an outdated look, and the team can't fix the root cause.
Two or three of these together usually justify an assessment.
Start with an assessment, not a rewrite
The instinct to throw the old app away and start fresh is strong, and often wrong. A legacy app encodes years of edge cases and business rules that are not written down anywhere else. Our assessment makes the trade-offs visible before you commit budget.
- 1
Code and architecture review
We map the modules, measure coupling, check test coverage and identify which parts are healthy and which are fragile.
- 2
Dependency and platform check
We list every framework, plugin and SDK with its support status, and confirm the app can still be built with current toolchains.
- 3
Feature and usage inventory
Using analytics where available, we find which features users actually rely on. Unused features are candidates to drop rather than migrate.
- 4
Recommendation and roadmap
You receive a recommended path, phased milestones, risks and an effort range for each option.
Rewrite vs refactor vs incremental migration
| Path | What it means | Works best when | Main risk |
|---|---|---|---|
| Refactor in place | Improve structure, update dependencies and add tests without changing the core stack | The language and framework are still supported and the architecture is salvageable | Underlying limits of the stack remain |
| Incremental migration | Replace the app screen by screen or module by module, with old and new code running together | The app is large, revenue-critical, or under active feature development | Running two technologies for a while adds build complexity |
| Full rewrite | Build a new app and switch users over at a planned release | The current stack is unsupported, the app is small, or the product itself is being redesigned | Feature parity takes longer than expected; hidden business rules get lost |
The strangler pattern on mobile
The strangler pattern replaces a system piece by piece until the old one can be removed. On mobile, that means new screens are built in the target technology and routed to from the existing app, while old screens are retired one at a time. Users keep getting updates throughout, and the business never waits months for a big switch.
Adding Flutter or React Native into a native app
Both frameworks support this officially. Flutter's add-to-app feature embeds Flutter screens inside an existing iOS or Android project, and React Native can be integrated into native apps the same way. This is a common route when you want to move to a shared codebase but can't stop shipping. Our React Native team and Flutter engineers both work this way, and our guide to choosing a cross-platform approach helps decide which target fits.
Migrating Objective-C to Swift and Java to Kotlin
Native apps from the early 2010s are often written partly or entirely in Objective-C or Java. Both still run, but most new platform APIs, sample code and libraries now target Swift and Kotlin, and modern UI toolkits (SwiftUI and Jetpack Compose) are built for them.
Objective-C to Swift
Swift and Objective-C interoperate in the same project, so we migrate file by file, starting with code that changes most often. Bridging headers keep both sides working together until the move is complete.
Java to Kotlin
Kotlin is fully interoperable with Java. Android Studio's converter gives a starting point, but we review every converted file for nullability and idiomatic style instead of committing the raw output.
UI layer
SwiftUI and Jetpack Compose can host and be hosted by older UIKit and View-based screens, so new UI can be introduced gradually alongside existing screens.
This work is a good fit for experienced iOS developers who are comfortable reading older code, not only writing new code.
Moving off Xamarin, Cordova and Ionic
Xamarin
Microsoft ended support for Xamarin on May 1, 2024. Unsupported apps stop receiving fixes and will fall behind new iOS and Android SDK requirements. The options are .NET MAUI, Microsoft's successor, which keeps C# and much of the business logic; or a move to native, Flutter or React Native. MAUI is often the shortest path for teams invested in .NET, though UI code and third-party components usually need significant rework either way.
Cordova and older Ionic apps
Apps built on Cordova, or on older Ionic versions that rely on it, run web code inside a WebView with plugins for device access. Many of those plugins are no longer maintained. Capacitor, from the Ionic team, is a common next step because it keeps the web codebase while modernizing the native layer. If performance or native feel is the core complaint, a move to Flutter, React Native or native code may be the better long-term choice.
Keeping users, data and ratings through the switch
A modernized app should arrive as an update to the existing one, not as a new listing. That keeps your installs, reviews and ratings, and search ranking history.
- Same identifiers: We keep the iOS bundle ID and Android application ID, and sign with the same keys or Play App Signing setup, so stores treat the release as an update.
- Local data migration: Users' stored data, such as offline records, settings and cached drafts, is moved from the old storage format to the new one on first launch, with tests on real upgrade paths.
- Sessions and credentials: We migrate Keychain and Keystore entries where possible so users are not forced to sign in again.
- Staged rollout: Google Play's staged rollouts and Apple's phased release let us release to a small share of users first and stop if crash rates rise.
- Feature flags and fallbacks: During incremental migrations, new screens sit behind remote flags so we can switch back without a new store release.
After the switch, we watch crash rates, reviews and key funnels closely, then hand the app over to your team or to our long-term maintenance service.