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Launch on iOS and Android From Shared Code

We pick between Flutter, React Native and Kotlin Multiplatform based on your product and team, then build one app that ships to both stores.

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Platform.kt
Sample code

Cross-platform development without picking the wrong framework

Cross-platform app development means writing most of your app once and running it on both iOS and Android. Modern options include Flutter, React Native and Kotlin Multiplatform, each with different strengths. Done well, the result looks and behaves like a native app while costing far less to build and maintain than two separate codebases with two separate teams.

The hard part is choosing. Flutter suits custom, brand-heavy interfaces and future web or desktop builds. React Native suits teams with React skills and products that share code with a website. Kotlin Multiplatform suits companies with an existing Android app that want to share business logic while keeping native UI. Pure native still makes sense for hardware-heavy or graphics-intensive apps, and a wrong early choice here is expensive to undo once the codebase grows.

Nexzem is framework-neutral. In the free consultation we look at your features, users, existing code and hiring plans, recommend one approach with reasons, and then deliver it in sprints with test builds on both platforms every couple of weeks. If you already have a native app, we can share logic gradually instead of starting over.

Read Cross-Platform, the way we write it

A short, idiomatic sample. Scroll and the editor types each part while the note beside it explains why it is written that way.

Platform.kt
Sample code
// commonMain: business logic written once for every platform
class Greeting(private val platform: Platform) {
fun greet(): String = "Hello from ${platform.name}"
}
// The shared code declares what it needs from each platform
expect class Platform() {
val name: String
}
// androidMain: the Android side of that contract
actual class Platform actual constructor() {
actual val name: String = "Android ${android.os.Build.VERSION.SDK_INT}"
}
// iosMain: the same contract, answered by UIKit
actual class Platform actual constructor() {
actual val name: String = UIDevice.currentDevice.systemName()
}

  1. line 1-5

    commonMain: business logic written once for every platform

  2. line 6-10

    The shared code declares what it needs from each platform

  3. line 11-15

    androidMain: the Android side of that contract

  4. line 16-19

    iosMain: the same contract, answered by UIKit

What we build with Cross-Platform

Shared-code mobile apps for iOS and Android, with the framework chosen to fit your team and roadmap.

  1. 01

    Framework Selection

    A short technical assessment comparing Flutter, React Native, Kotlin Multiplatform and native for your features, team skills and long-term maintenance cost.

  2. 02

    Flutter App Builds

    Dart codebases for apps that need a distinctive custom UI across iOS, Android and optionally web or desktop from one project.

  3. 03

    React Native App Builds

    TypeScript apps that share logic and developer skills with your React or Next.js website, with native modules where performance demands it.

  4. 04

    Kotlin Multiplatform Logic

    Shared networking, data and business rules in Kotlin used by native Android and iOS interfaces, ideal for teams with existing native apps.

  5. 05

    Hybrid App Replacement

    Rebuilds of slow Cordova or Ionic web-view apps into modern cross-platform frameworks, migrating users and data without losing store ratings.

  6. 06

    Backend and Admin Panels

    APIs, dashboards and content tools that power the mobile app, built in Node.js or Python and hosted on AWS, Azure or Google Cloud.

  7. 07

    Dual Store Releases

    Coordinated App Store and Play Store submissions, beta testing groups and release notes so both platforms receive features on the same day.

Why teams pick Nexzem for Cross-Platform

The checks every engagement has to pass before we call it done.

.github/PULL_REQUEST_TEMPLATE.md5/5 checked

  • - [x] Lower build and upkeep cost

    Shared code means one team, one set of tests and one bug fix that lands on both platforms.

  • - [x] Feature parity

    iOS and Android users get the same features at the same time, which simplifies support and marketing.

  • - [x] Unbiased framework advice

    We work in Flutter, React Native and native code, so our recommendation follows your needs, not our habits.

  • - [x] Native escape hatches

    Where shared code falls short, we write Swift or Kotlin for that feature instead of compromising the experience.

  • - [x] Easier team growth

    One skill set to hire for and one codebase to onboard into, whether you scale with us or in-house.

A decision framework for native vs cross-platform

The choice is less about technology fashion than about where your product's value lies. If it lives in business logic, content, forms, commerce and standard device features, cross-platform frameworks deliver native-quality results with one team. If it lives in deep platform integration, heavy graphics or features that appear on day one of each OS release, native development earns its extra cost.

Our native vs cross-platform comparison discusses the trade-offs in detail. In practice, we score each product against a short list of criteria and often land on a hybrid: a cross-platform core with small native modules for the few capabilities that need them.

Team continuity matters as much as framework features. A cross-platform app maintained by a stable team that knows it well will outperform a theoretically better native setup that nobody can staff. Factor hiring, onboarding and long-term support into the decision, not only the first release.

  • How much of the app is shared logic versus platform-specific UI?
  • Which native SDKs and device features are essential?
  • How custom and animation-heavy is the design?
  • What skills does the team already have, and who will maintain the app?
  • Is there a web app that could share code with mobile?
  • How quickly must new OS features be supported?
  • How long will the app be maintained, and by whom?

How we structure a cross-platform project

We define early which code is shared and which is platform-specific. Business logic, data access, validation and most screens are shared, while payments, background tasks, widgets and certain hardware integrations live in clearly isolated native modules with their own tests. That boundary keeps the shared codebase clean and makes native work predictable.

The design system adapts to platform conventions where users expect them, such as navigation patterns, date pickers and back behavior, while keeping brand components consistent. CI builds and signs both apps from every merge, runs automated tests and distributes builds to testers on TestFlight and Google Play internal testing.

For organizations with strong native teams, Kotlin Multiplatform offers another path: sharing business logic written in Kotlin while each platform keeps a fully native interface. It suits banks and enterprises that want consistency in rules without changing how their UI teams work.

Cost drivers of a cross-platform project

Sharing code reduces effort, but scope is still driven by the product. These factors have the largest influence on timeline and budget, and agreeing them before design begins prevents surprises in the middle of the build. Each also affects how much testing the release needs.

  • Number of screens, user roles and admin features.
  • Native modules for payments, maps, Bluetooth or camera features.
  • Offline mode and data synchronization complexity.
  • Backend and integrations with existing systems.
  • Design customization and animation.
  • Device testing range and accessibility requirements.
  • App store compliance and post-launch maintenance.
  • Analytics, crash reporting and release automation.

How Cross-Platform projects run

$ git log --graph --oneline main..delivery

  1. b8329d1

    feat: assess and recommend

    We review features, users and existing systems, then recommend a framework with clear trade-offs.

  2. a0d7a72

    feat: design for both platforms

    Figma designs that respect iOS and Android conventions where they differ and stay shared where they do not.

  3. 6cac109

    feat: build with shared tests

    Sprint development with automated tests that run against both platform builds.

  4. c89c17c

    feat: release together

    Parallel store submissions and staged rollouts so both audiences receive the launch on schedule.

  5. 28637e1

    merge: support and scale

    Ongoing updates, OS compatibility work and new features through maintenance or a dedicated team.

What teams build with Cross-Platform

  • Startup MVP on both app stores

    A startup validates its idea on iOS and Android at once with one small team, shipping a cross-platform MVP in weeks and iterating weekly based on usage data instead of maintaining two separate codebases.

  • Replacing an aging hybrid app

    An enterprise replaces a slow Cordova-based field app with a React Native or Flutter rebuild, keeping the same backend APIs while improving speed, offline behavior and access to modern device features.

  • Shared banking logic with native interfaces

    A bank uses Kotlin Multiplatform to share validation, calculation and security logic across its iOS and Android apps, while each platform team keeps building fully native screens with SwiftUI and Jetpack Compose.

  • Retail loyalty app

    A retail chain launches a loyalty app with digital cards, offers, purchase history and store locator on both platforms, integrated with its POS and CRM, and updated frequently as campaigns change.

  • Telehealth app for patients

    Patients book appointments, join video consultations, receive prescriptions and upload reports from one cross-platform app, with native modules for video and secure storage meeting healthcare data requirements on both platforms.

Where Cross-Platform sits in your stack

The tools we pair it with, layer by layer. Select a layer to see what it is responsible for.

Technologies often used with Cross-Platform

All 32 technologies

More in Mobile

Cross-Platform development FAQs

Something else on your mind? Ask a consultant and get a reply within one business day.

Flutter or React Native: which should we choose?

Flutter is usually better for custom visual design and future web or desktop builds. React Native is usually better if your developers know React or you want to share code with a website. Both handle typical business apps well, and we recommend one after looking at your specifics.

When is cross-platform the wrong choice?

If your app is built around advanced camera processing, AR, heavy 3D graphics or tight hardware control, native development is often safer. The same applies when you only target one platform. We will tell you if that is your situation.

How much can cross-platform save compared with two native apps?

Savings depend on how much of the app is shared, and most standard screens and logic are. The cost drivers are feature count, custom native modules, backend work and design. We give a fixed quote after a free consultation.

Will users notice the app is not native?

Not for typical business and consumer apps built carefully. We follow each platform's navigation and gesture conventions and profile performance before release.

Can you continue an existing hybrid or cross-platform app?

Yes. We audit the code and dependencies first, then either stabilise and extend it or propose a phased migration if the current framework is holding you back.

What is Kotlin Multiplatform and when does it fit?

Kotlin Multiplatform lets teams share business logic written in Kotlin across Android, iOS and other targets while keeping native user interfaces, or optionally sharing UI with Compose Multiplatform. It fits organizations with strong Android teams that want consistent logic without adopting a new UI framework.

How do you handle design differences between iOS and Android?

We keep brand elements consistent and adapt interaction patterns to each platform where users expect them, such as navigation, gestures, system dialogs and pickers. Both Flutter and React Native support platform-aware components, so one codebase can feel natural on each device.

We work with clients across the USA, UK, Australia, UAE, New Zealand and India.

Where we work

Tell us what you're building.

A solutions consultant replies within one business day with a recommended stack, a rough estimate and a suggested team.

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