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Cross-Platform App Development

The cross-platform app development company that tells you when not to hire one

BinaryBrill is a cross-platform app development company delivering React Native app development services and Flutter builds from a single codebase that ships to both stores, with native modules written in wherever the framework runs out. Hire cross-platform developers — in-house senior engineers — when your app is mostly screens, data and workflow, and expect a plain answer when your requirements put a shared codebase out of reach.

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A senior engineer replies within 24 hours — not a sales rep.

Where cross-platform builds quietly stop paying off

The shared-code percentage keeps falling, one exception at a time

It started at ninety percent shared. Then came a native payment sheet, a platform-specific permissions flow, a map component, and a performance fix that had to be written twice. Each exception was reasonable alone; together they mean you're maintaining three codebases instead of one, without ever deciding to.

A requirement arrives that the framework can't reach

Background audio that survives a locked screen, tight camera control, or a wearable companion turns up in month nine, after the framework was chosen for its speed rather than its ceiling. Now the roadmap is native bridge work on top of the cross-platform build, and you're paying the overhead of both approaches without the saving of either.

React Native or Flutter was picked because it was familiar, not because it fit

The choice between the two often comes down to which one a founding engineer already knew, not which one matches the app's actual demands or the team that will maintain it afterwards. That's a fine reason to start fast and a poor reason to be stuck with the decision for three years.

An OS update breaks the one native module holding it together

The app is mostly framework code, except for the one hand-written native module doing the hard part — and that module is exactly what breaks when Apple or Google changes something underneath it. Nobody budgeted maintenance for a bridge that only its original author fully understands.

How a cross-platform app development company should choose and build

The question isn't which framework is better in the abstract — it's whether your app's requirements sit comfortably inside what a shared codebase can do, and for how long. We answer that before we write the proposal, not after we've sold you the build.

We check the requirement list against the framework's ceiling first

Every capability the product needs now, and plausibly needs next year, gets checked against what React Native and Flutter support without a bridge. Where the list stays inside that boundary, cross-platform is the honest recommendation. Where it doesn't, we say so before you've paid for a build you'll partly redo.

React Native or Flutter, chosen against your team, not our preference

React Native fits teams with existing JavaScript or React skills and a need to lean on a wide ecosystem of existing packages. Flutter fits teams prioritising one rendering engine and near-identical UI across both platforms. We recommend on your hiring reality and long-term maintenance, not on which one we'd rather build in.

Native module boundaries agreed before the first sprint

Where the framework will need a native bridge — payments, a specific sensor, a background service — that boundary is designed up front, so the platform-specific work is a planned line item rather than an emergency rewrite discovered in testing.

Shared logic, platform-correct interface

Business logic, data layer and navigation structure are shared; the interface still respects each platform's own conventions for gestures, date pickers, share sheets and permission prompts, so neither iOS nor Android users feel they got the other platform's app in a different colour.

What this covers

Pick the piece you need, or bring us the problem and we'll tell you which applies.

React Native App Development Services

Builds on React Native and Expo for teams with existing JavaScript or React skills, or who want to draw on a wide package ecosystem for maps, payments and native integrations rather than writing everything from scratch.

Expo-managed or bare workflow chosen against how much native code the project will eventually need
TypeScript throughout, with shared business logic and a typed API contract
React Navigation with platform-correct gestures, transitions and share sheets on both stores
Over-the-air updates for JavaScript-layer fixes without waiting on App Store or Play review

Flutter App Development

Builds on Flutter for teams prioritising one rendering engine and near-identical visual output across iOS and Android from a single Dart codebase — the choice a Flutter app development company relationship usually makes sense for.

Widget-based UI with a design system that renders identically on both platforms, styled to feel native where it matters
State management with Riverpod or Bloc chosen for the app's actual complexity, not by default
Platform channels built deliberately where Flutter needs a native capability

Hire Cross-Platform Developers

Dedicated React Native or Flutter engineers who join your sprints and your code review, sized up or down as the roadmap changes, without you running a separate hiring pipeline for a skillset you may only need for one project.

Senior cross-platform engineers embedded in your existing team and tooling
Scale from one engineer to a full team without a second procurement cycle
Direct communication with the engineer doing the work, not an account manager relaying updates

Native Module & Bridge Development

Where React Native or Flutter can't reach a capability directly — a payment sheet, a Bluetooth peripheral, a background service — we write the native Swift or Kotlin module and the bridge that exposes it cleanly to the shared codebase, with the boundary documented so it doesn't become a black box.

Native modules written in Swift and Kotlin, exposed through a typed bridge rather than an ad hoc one
Boundaries planned during architecture, not improvised when a feature request arrives
Documentation so the module survives a framework upgrade or a change of engineer

Cross-Platform App Modernisation & Native Migration

For apps where the shared-code percentage has fallen further than anyone planned, or the React Native or Flutter version is several majors behind. We assess what's actually salvageable, upgrade what can be upgraded, and are direct about which parts have earned a native rewrite.

Framework version upgrades — React Native, Expo SDK, Flutter — assessed for breaking changes before they're applied
An honest read on which native workarounds have accumulated past the point of being worth maintaining
A migration path to native for the specific module that needs it, without discarding the shared code that still works

The stack we build on

Chosen to fit the problem — not because it's what we used last time.

React Native

React Native
Expo
TypeScript
React Navigation
Zustand

Flutter

Flutter
Dart
Riverpod
Bloc
GoRouter

Native bridge & modules

Kotlin Multiplatform
Native Modules (Swift)
Native Modules (Kotlin)
Turbo Modules

Testing & release

Detox
Jest
Fastlane
EAS Build
App Store Connect & Play Console

How we'll work together

Every stage ends with something in your hands — not a status update.

01
Framework fit assessment
We check the product's capability list against what React Native and Flutter can reach without a bridge, weigh that against your team's existing skills, and give you a direct recommendation — including a recommendation against cross-platform where the requirements justify it.
You get: A written recommendation (React Native, Flutter, or native), the reasoning behind it, and a cost comparison against the routes we ruled out.
02
Architecture and native module boundary
We draw the line between shared and platform-specific code before any of it is written, and design the native escape hatch in from the start, so the first platform-specific requirement isn't a crisis.
You get: An architecture document, a native module boundary map, and an agreed device and OS support matrix.
03
Build with both stores running in parallel
Signed builds go to TestFlight and Play internal testing from the first sprint, on both platforms at once, so a parity gap between iOS and Android is caught the week it appears rather than at release.
You get: Installable builds on both platforms every sprint, a CI pipeline with signing configured, and code in your repository throughout.
04
Device verification and dual-store release
Testing across the real device matrix on both platforms, an over-the-air update channel configured for JavaScript-layer fixes, then submission to both stores with the material each expects.
You get: Device test results against the agreed matrix, published listings on both stores, and signing assets transferred into your own developer accounts.

Where we've applied this

Retail & e-commerce

Shopping and content apps that are mostly screens and data, where a single codebase gets both stores updated on the same day.

Booking & marketplace platforms

Workflow-heavy apps — search, listings, booking flows — that rarely touch the hardware in ways React Native or Flutter can't handle directly.

Media & content

Feed and content-consumption apps where shared business logic and a consistent design system matter more than platform-specific rendering.

Field operations (light)

Form and workflow apps for staff that don't need rugged-device or deep sensor access, where cross-platform keeps two platforms in step for less.

Early-stage startups

Products validating a market before committing to a platform split, where one team shipping to both stores from day one preserves runway.

Internal enterprise tools

Staff-facing apps with modest hardware requirements, where a shared codebase means one bug fix instead of two.

Questions buyers ask us

Should we build in React Native or Flutter?

It depends on your team more than on either framework's technical merits. React Native is the better fit if you already have JavaScript or React engineers and want to draw on its wide package ecosystem. Flutter suits teams who value one rendering engine producing near-identical output on both platforms and are comfortable hiring for Dart. We're a React Native app development shop as much as a Flutter app development company — the recommendation comes from your constraints, not ours.

Is cross-platform actually cheaper than building native for both platforms?

For the initial build, usually — roughly one team instead of two, and a single QA pass over shared logic. Across the product's life the maths is less obvious: every native module you end up writing costs twice, and you inherit a dependency on a framework whose upgrade cycle you don't control. If the app is screens, data and workflow, cross-platform saves real money. If it leans on the hardware, look at our iOS App Development and Android App Development pages instead — the saving tends to evaporate around the second year.

How do we know if our app is a good fit for a single codebase?

List every OS-level capability the app needs now and plausibly needs next year — background audio, tight camera control, wearable support, deep biometric integration — and check it against what React Native and Flutter support without a bridge. If the list stays inside that boundary, you're a good fit. If two or three items fall outside it, the honest conversation is about how much bridge work you're signing up for.

What drives the cost of a cross-platform build, and how long does it take?

Screen count matters less than people expect. The expensive things are offline behaviour, real-time features like chat or live tracking, payment flows, and any native module the framework can't reach directly. After a shaping conversation we can give you a range, and a short paid discovery converts that into a fixed scope and timeline.

How do you handle data privacy in a shared codebase?

Sensitive data still goes through each platform's own secure storage — Keychain on iOS, Android Keystore on Android — rather than a JavaScript-layer store, and third-party packages are vetted before they're added to the dependency tree. Your data and your users' data stay in your own infrastructure and accounts throughout.

When should we not use React Native or Flutter?

When the product's core value depends on tight hardware access — sustained background processing, heavy camera or sensor control, or an interface that has to feel indigenous to one platform. In those cases native on the platform your users are actually on is the honest answer, even though it costs more; see our iOS App Development and Android App Development pages for that route.

Can you migrate our React Native or Flutter app that's fallen behind on framework versions?

Yes — we start with an assessment of how far behind the framework version is, what's blocking the upgrade, and which native workarounds have accumulated past the point of being worth maintaining. From there we upgrade what's salvageable and migrate to native only the specific pieces that have genuinely earned it, rather than discarding shared code that still works.

Who owns the app, the code and the store accounts?

You do, from the first commit: repository, designs, signing certificates and both store listings. We publish under your own Apple and Google developer accounts rather than ours, because moving a live app out of an agency account later is genuinely painful. If those accounts don't exist yet, we help you set them up before submission.

Who writes the code, and where are they based?

Our own in-house engineers in Sahibzada Ajit Singh Nagar, Punjab — 45+ of them, with over a decade of combined delivery experience, delivering for clients in 15+ countries. Nothing is subcontracted. You meet the engineers who will be on your project before you sign, and the person demonstrating the work each sprint is the person who built it.

Not sure if a single codebase covers your app?

Tell us what the app needs to do on each platform. A senior engineer replies within 24 hours with a straight recommendation — React Native, Flutter, or native — and the reasoning behind it.

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