App Modernization Services React Native to Swift and Kotlin Migration for iOS and Android

App modernization moves an existing mobile app to a current, supported technology stack without losing its users, data, or store listing. StudioKrew migrates React Native, Flutter, Xamarin, Cordova, and Ionic apps to native Swift and Kotlin, upgrades Objective-C and Java code, and moves legacy PHP backends to Node.js. Fixed-scope migrations are quoted after an audit of your app, dedicated developers cost $18 to $55 per hour, and you receive a scoped written proposal within 48 hours.

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Key Facts App Modernization at StudioKrew, at a Glance

A short, factual snapshot of what we migrate, how we price it, and how we protect your users during the move.

Migration paths

React Native, Flutter, Xamarin, Cordova, and Ionic to native Swift and Kotlin. Objective-C to Swift, Java to Kotlin, and PHP backends to Node.js.

Pricing

Fixed-scope migrations are quoted after an audit. Dedicated developers cost $18 to $55 per hour; dedicated teams cost $15,000 to $40,000 per month.

Proposal in 48 hours

Every inquiry gets a scoped written proposal within 48 hours, with the recommended path and the risks we found.

Your listing stays yours

The native app ships as an update to your existing App Store and Google Play listings, so installs, ratings, and reviews stay in place.

Experience

12+ years since 2013, 250+ apps and software products delivered, and a team of 100+ specialists.

Offices and markets

New Delhi, Chicago, Oakville, and Dubai, serving the USA, UK, Europe, Australia, India, UAE, and South Africa.

Overview What App Modernization Services Cover

Most mobile apps outlive the technology choices made at launch. A framework that helped a startup ship its first version fast can later slow every release. Performance hits a ceiling on older devices, bridges break with each OS update, plugins lose their maintainers, and fewer developers want to work on the codebase.

App modernization services fix that without starting the business over. We keep what works (your users, data, store presence, and business logic) and replace what holds the product back. The result is a native iOS app in Swift, a native Android app in Kotlin, and a backend that can carry the next few years of growth.

What is app modernization?

App modernization is the process of moving an existing app to a current, supported technology stack. For mobile apps it usually means rewriting cross-platform or legacy code in native Swift for iOS and Kotlin for Android, rebuilding the interface in SwiftUI and Jetpack Compose, and updating the backend, while the app keeps its users, data, and store listing.

Why Teams Are Moving to Native Now

When Airbnb moved away from React Native, it gave many product teams permission to question the shared-codebase promise. Our breakdown of why Airbnb moved from React Native to Swift and Kotlin covers what they learned and what it means for smaller teams.

Other pressures are more direct. Microsoft ended support for Xamarin on May 1, 2024, so Xamarin apps no longer get fixes for new iOS and Android releases. Apple and Google raise their minimum SDK requirements for store submissions every year, and apps held together by old plugins fall further behind with each cycle. New platform features, such as widgets, Live Activities, on-device AI, and the latest camera and health APIs, arrive in Swift and Kotlin first.

None of this means every app should be rebuilt. It means the decision deserves an honest audit, which is where every engagement with us starts.

Our App Modernization Services

Every engagement starts with an audit of your codebase, backend, and store setup. These are the migrations we run most often. If you need a new app rather than a migration, see our native app development services.

React Native to Swift and Kotlin

We rebuild React Native apps as native iOS and Android apps, screen by screen or in one release. Business logic, API contracts, and analytics events are mapped first, so the native app behaves like the one your users already know. Our Swift app development and Kotlin app development teams work in parallel.

Flutter, Cordova, and Ionic to Native

Hybrid and WebView-based apps hit limits with animation, offline behavior, and device APIs. We move them to native Swift and Kotlin and replace each plugin with a maintained native equivalent, or with our own code where none exists.

Xamarin to .NET MAUI or Native

With Xamarin out of support, you have two paths: move to .NET MAUI and keep your C# code, or rebuild natively for full platform access. We assess both against your roadmap and team, then recommend one.

Objective-C to Swift, Java to Kotlin

For native apps written years ago, we convert Objective-C to Swift and Java to Kotlin module by module. Both languages run side by side with their predecessors, so the app stays shippable at every step of the move.

UI Modernization with SwiftUI and Jetpack Compose

We rebuild dated interfaces in SwiftUI and Jetpack Compose, add dark mode and accessibility support, and set up a design system your own team can extend after handover.

Backend Modernization: PHP to Node.js

Many apps sit on a PHP backend that struggles as usage grows. We move it to Node.js on the MERN stack (MongoDB, Express, React, Node.js) or another architecture that scales across multiple instances, with the API versioned so older app releases keep working.

Data, Release, and User Migration

We migrate local data, sessions, and settings on first launch, keep push notification tokens and deep links working, and release through phased rollouts so any issue reaches a small share of users first.

Support After Migration

Once the native app is live, our application maintenance and support team handles OS updates, monitoring, and new features under a separate agreement.

Migration Paths What We Migrate, and Why Teams Move

Each path has its own risks and effort. This is how we approach the most common ones.

From	To	Why teams move	What we watch for
React Native	Swift (iOS) and Kotlin (Android)	Performance, native UI, and faster access to new OS features	Bridge-dependent libraries, shared business logic, over-the-air update setups
Flutter	Swift and Kotlin	Platform-specific UI and deeper OS integration	Custom rendering, platform channels, state management patterns
Xamarin	.NET MAUI, or Swift and Kotlin	Microsoft ended Xamarin support on May 1, 2024	Custom renderers, third-party Xamarin components, C# business logic worth keeping
Cordova and Ionic	Swift and Kotlin	WebView performance, plugin maintenance, offline behavior	Plugins with no maintained equivalent, local storage, hybrid navigation
Objective-C	Swift	Maintainability, hiring, and access to modern Apple APIs	Mixed-language bridging, legacy memory management code
Java (Android)	Kotlin	Maintainability, Jetpack Compose, and coroutines	Null safety changes, legacy threading code
PHP backend	Node.js (MERN stack) or another scalable architecture	Load, response times, and scaling across instances	API compatibility for older app versions, data migration, zero-downtime cutover

Not sure which path fits your app? Our mobile app development company team reviews your current setup and recommends one in the written proposal.

Decide Should You Migrate? Three Options Compared

Migration is not always the right answer. When a client's current stack still serves them, we say so.

Option	When it fits	Main trade-off
Stay cross-platform and improve	The app performs acceptably, the team knows the framework, and the roadmap needs no deep platform features. Our React Native app development team handles upgrades and performance work.	Platform limits remain, so you treat symptoms rather than the cause.
Incremental migration	The app is large, releases cannot stop, and some screens matter far more than others. Native screens replace old ones inside the existing app, one area at a time.	Two technologies live side by side for a while, which needs a careful build and release setup.
Full native rebuild	The codebase is hard to change, performance problems are structural, or the app needs features only native code can reach.	A larger effort up front, and feature work slows during the rebuild.

Cross-platform still suits many products. If you are starting a new app and want one codebase, read about our cross-platform app development approach.

Process How We Run a Migration

Codebase and backend audit

We review the code, dependencies, backend, analytics, and store setup, and list every screen, integration, and third-party SDK. You get a written audit with the risks we found and a recommended path.
Migration plan

We choose between an incremental migration and a full rebuild, set the order of screens, and agree acceptance tests based on how the current app behaves today.
Parallel build

The native apps are built while your current app keeps shipping. API contracts and analytics events are fixed early, so both versions report the same data.
Data and user migration

We write the code that moves local data, sessions, and settings on first launch, and test upgrades from older app versions on real devices.
Phased release

The native app ships as an update to your existing listings, through phased release on the App Store and staged rollout on Google Play, with crash and performance monitoring from day one.
Stabilize and hand over

After release we fix issues from the rollout, hand over the source code and documentation, and, if you want, continue under a maintenance agreement.

Pricing App Modernization Pricing and Engagement Models

Two apps with the same number of screens can need very different effort once their dependencies, backend, and test coverage are on the table. So we quote fixed-scope migrations after an audit, and the written proposal arrives within 48 hours of your inquiry.

Fixed-scope migration

Quoted after audit

One app or one migration path, with clear screens, integrations, and acceptance tests.

Request Proposal

Dedicated developer

$18 to $55 per hour

Swift, Kotlin, or Node.js capacity added to your own team for an incremental migration.

Dedicated team

$15,000 to $40,000 per month

Full rebuilds of large apps, or iOS, Android, and backend work moving at the same time.

Support after migration

Quoted after scoping

OS updates, monitoring, and new features once the native app is live.

Experience Native Rebuilds From a Team That Has Shipped 250+ Apps

Our developers have rebuilt existing apps natively for clients who needed better performance, deeper access to device features, or a codebase they could hire for. We do not name those clients on this page, and we are happy to walk you through the relevant work on a call.

Since 2013 StudioKrew has delivered 250+ apps and software products. The same Swift, Kotlin, and backend engineers who build our new native apps run our migrations, so your rebuilt app gets the standards of a new build, not a patch job.

Brands we have built apps for

Technology The Stack We Migrate To

Native iOS apps in Swift with SwiftUI and UIKit, native Android apps in Kotlin with Jetpack Compose, .NET MAUI where keeping C# is the better fit, and backends on Node.js with Express and MongoDB, deployed on AWS or Azure.

iOS
Swift
SwiftUI
Firebase
Node.js
Redis
AWS
Azure

Insights Read Before You Decide

Why Airbnb Moved from React Native to Native Swift and Kotlin

What Airbnb learned from running React Native at scale, and which of those lessons apply to smaller product teams.

React Native vs Swift and Kotlin: Which Should You Pick for Your Next App?

The key differences between React Native and native development, OS compatibility challenges, and why some startups are moving back to native.

Why Swift Can Be the Right Mobile App Development Framework for Your Business

When Swift is the right choice for an iOS app, and what it means for performance, maintenance, and hiring.

FAQ Frequently Asked Questions: App Modernization

Common questions from CTOs and product leads weighing a migration. Have a specific app in mind? Request a free consultation with our team.

App modernization services move an existing mobile app to a current, supported technology stack without losing its users, data, or store listing. That usually means rewriting cross-platform or legacy code in native Swift and Kotlin, updating the interface to SwiftUI and Jetpack Compose, and modernizing the backend the app depends on.

Migrate when performance problems are structural, when you need platform features that React Native reaches late or not at all, or when library and upgrade issues slow every release. If the app performs well and the roadmap needs no deep platform work, improving the React Native app is often the better investment. Our audit tells you which case you are in.

We quote fixed-scope migrations after an audit, because cost depends on the number of screens, the third-party SDKs, the backend changes, and the existing test coverage. You receive a scoped written proposal within 48 hours of your inquiry. For ongoing work, dedicated developers cost $18 to $55 per hour and a dedicated team costs $15,000 to $40,000 per month.

The timeline depends on the number of screens, the integrations and SDKs involved, whether the backend changes too, and how much testing older app versions need. An incremental migration puts the first native screens in front of users earlier than a full rebuild. We set out the schedule in the written proposal after the audit.

Not when the migration is planned properly. The native app ships as an update to your existing App Store and Google Play listings, so installs, ratings, and reviews stay in place. We migrate local data and sessions on first launch and use phased releases, so any issue reaches a small share of users first.

Microsoft ended support for Xamarin on May 1, 2024. You can move to .NET MAUI, which keeps your C# code and your team's skills, or rebuild natively in Swift and Kotlin for full platform access. We compare both against your roadmap, budget, and team before recommending one.

Yes. We move legacy PHP backends to Node.js on the MERN stack, or to another architecture that scales across multiple instances. The API is versioned so older app releases keep working while users update, and the cutover is planned to avoid downtime.

We stay on through stabilization, fix any issues from the rollout, and hand over the source code and documentation. If you want ongoing help, our maintenance team handles OS updates, monitoring, and new features under a separate agreement.

App Modernization Services React Native to Swift and Kotlin Migration for iOS and Android

Key Facts App Modernization at StudioKrew, at a Glance

Migration paths

Pricing

Proposal in 48 hours

Your listing stays yours

Experience

Offices and markets

Overview What App Modernization Services Cover

What is app modernization?

Why Teams Are Moving to Native Now

Our App Modernization Services

React Native to Swift and Kotlin

Flutter, Cordova, and Ionic to Native

Xamarin to .NET MAUI or Native

Objective-C to Swift, Java to Kotlin

UI Modernization with SwiftUI and Jetpack Compose

Backend Modernization: PHP to Node.js

Data, Release, and User Migration

Support After Migration

Migration Paths What We Migrate, and Why Teams Move

Decide Should You Migrate? Three Options Compared

Process How We Run a Migration

Codebase and backend audit

Migration plan

Parallel build

Data and user migration

Phased release

Stabilize and hand over

Pricing App Modernization Pricing and Engagement Models

Fixed-scope migration

Dedicated developer

Dedicated team

Support after migration

Experience Native Rebuilds From a Team That Has Shipped 250+ Apps

Brands we have built apps for

Technology The Stack We Migrate To

Insights Read Before You Decide

Why Airbnb Moved from React Native to Native Swift and Kotlin

React Native vs Swift and Kotlin: Which Should You Pick for Your Next App?

Why Swift Can Be the Right Mobile App Development Framework for Your Business

FAQ Frequently Asked Questions: App Modernization

What are app modernization services?

Should we migrate from React Native to native Swift and Kotlin?

How much does app modernization cost?

How long does a React Native to native migration take?

Will we lose users, ratings, or data when we migrate?

Our app is built on Xamarin. What are our options?

Can you modernize our PHP backend at the same time?

What happens after the native app goes live?

Tell Us What Your App Runs On Today

StudioKrew: Native App Modernization Experts

We design & develop with beauty and brain.