Migrating a Native App to React Native and Expo: A Comprehensive Guide

Why 2026 Is the Right Time to Migrate a Native App to React Native

Migrating a native app to React Native is no longer a leap of faith — it is a matured engineering decision. React Native 0.76 made the New Architecture the default for new projects; the legacy architecture was first frozen and has since been removed from current releases. A new React Native project today runs bridgeless, and Expo SDK 57 ships the current React Native release out of the box. The old "bridge performance" objection — the strongest argument against migration for years — is effectively settled.

For companies maintaining two codebases with separate Swift and Kotlin teams, that raises a concrete question: has the cost of unifying iOS and Android into one codebase finally dropped below the cost of keeping two apps alive? This guide covers the decision framework, the two main migration strategies, a phased plan, the pitfalls we see most often, and realistic time and cost expectations.

Before You Migrate: X-Ray Your Existing App

A one-week discovery phase prevents a months-long misdirected investment. Score these four areas:

• Codebase health: Are layers cleanly separated, or is business logic welded into view controllers? A well-structured app suits incremental migration; an app drowning in technical debt is often cheaper to rewrite.
• Dependency inventory: List every native SDK you use and check its React Native equivalent on reactnative.directory. Every SDK without an equivalent is a module you will bridge yourself — the most underestimated line item in any migration budget.
• Team profile: Does the team have React/TypeScript experience? Will your native developers stay involved? The biggest advantage of the brownfield approach is that it introduces React Native gradually without changing how native teams operate.
• Product roadmap: If major feature deliveries are due in the next six months, a full rewrite will stall them; incremental migration can run in parallel with delivery.

The Two Main Strategies: Full Rewrite vs. Brownfield

Criteria	Full Rewrite (Greenfield)	Brownfield / Incremental
Approach	Rebuild the app from scratch with Expo/React Native; replace the old app when ready	Integrate React Native into the existing native app screen by screen
Upfront cost	High — double maintenance until the first release ships	Low — the first screen can be in production within weeks
Risk profile	Big bang: all risk concentrates at one cutover moment	Distributed: each screen is validated separately and easy to roll back
Impact on delivery	Can pause the roadmap	Runs in parallel with delivery
When it makes sense	Codebase is past its useful life; app is small to mid-sized	App is large, alive, and revenue-generating; delivery cannot stop
End state	One clean codebase	Mixed codebase during migration; the goal is still one codebase

A Decision Tree

1. Small or mid-sized app (under ~30 screens) with heavy technical debt? → Full rewrite. Porting a decayed architecture costs more than rebuilding it.
2. Large, actively developed, revenue-generating product? → Brownfield. Distribute the risk screen by screen.
3. Native team staying, but you want to evaluate React Native? → Brownfield pilot: start with one low-risk screen (settings, help, a campaign page).
4. Proven product idea, but an unmaintained codebase and a dissolved team? → Full rewrite, using the existing app as your behavioral specification.

Brownfield Migration: A Step-by-Step Plan

The most mature tooling for incremental migration today is the React Native Brownfield v3 approach with its Expo config plugin: the React Native side is packaged into a single artifact (an XCFramework for iOS, an AAR for Android) and added to the native project like any ordinary library. The native team keeps its build process; the React Native team works with Expo tooling on its own side.

1. Pilot screen (2-4 weeks): Pick a low-risk, measurable screen. The goal is technical validation: the navigation bridge, theming, and crash telemetry.
2. Bridge contracts: Consolidate all data exchange between native and React Native (session, user, theme, deep links) into one type-safe contract layer. Getting this layer right early is the foundation for every screen that follows.
3. Component library: Rebuild your design system as React Native components so every new screen draws from it.
4. Feature slices: Progress by end-to-end feature slices (say, the entire "profile" flow) rather than isolated screens — and build all new features in React Native only. The migration starts paying for itself.
5. Cutover and cleanup: Critical flows (onboarding, checkout, the main feed) go last. When the final native screen retires, strip the brownfield shell and settle into a pure React Native/Expo project.

Industry experience shows a first screen can reach production within about a month. For staged rollouts and fast rollback practices during cutover, see our article on progressive delivery and feature flags.

The Full Rewrite Roadmap: Starting Fresh with Expo

For a full rewrite in 2026, Expo is the standard choice: file-based routing (Expo Router), cloud builds (EAS Build), store submission (EAS Submit), and OTA updates (EAS Update) form a single chain. The roadmap:

1. Inventory every screen and behavior of the existing app — the old app is your written requirements document.
2. Rank screens by real usage from analytics and scope only the core flows into the first release. Not porting unused screens is the hidden profit line of a rewrite.
3. Set up the Expo project with TypeScript, Expo Router, and design-system foundations. For structuring navigation at scale, see our React Native navigation architecture guide.
4. Cover native SDK needs from the Expo module ecosystem; write native modules for the rest (next section).
5. Run betas through TestFlight and Play Console test tracks, then replace the old app with a staged rollout rather than a single cutover.

Store-side requirements — privacy manifests, Data Safety, account deletion — await you in a rewrite too; we covered them in our App Store and Google Play publishing guide.

Bridging Native Modules: Turbo Modules and Expo Modules

SDKs without a React Native equivalent are the most technical part of any migration. Under the New Architecture, native modules are called through Turbo Modules — directly via JSI, without the old bridge's serialization cost — with type-safe interfaces generated by codegen. In Expo projects, the Expo Modules API offers a modern, low-ceremony layer for writing modules in Swift and Kotlin. Our practical rules:

• Search for a community package first; if none exists, wrap only the SDK surface you actually use — never the whole SDK.
• Reconcile platform differences in the TypeScript contract, not in native code.
• Write native unit tests and JS contract tests for every bridged module.

For a deeper look at how the New Architecture works under the hood, see our article on React Native's New Architecture and the Fabric renderer.

Common Pitfalls and How to Avoid Them

• Skipping the dependency audit: The most expensive surprises come from discovering an unbridgeable SDK mid-migration. Complete the inventory in discovery week.
• Underestimating the navigation bridge: In brownfield setups, transitions between the native stack and React Native navigation (back-button behavior, deep links, modal stacks) produce more bugs than any other boundary. Validate it first, on the pilot screen.
• Duplicating session and state: Auth tokens, user state, and feature flags must be read from a single source across both worlds; keeping two session copies invites sync bugs.
• Migrating without baselines: Measure startup time, screen transitions, and frame rates on the native app before you start, and compare the same metrics per slice. "It got slower" debates only end with data.
• Trusting legacy-era guides: Much of the internet's migration advice predates the New Architecture. The legacy architecture is gone in 2026 — verify that any guide you follow was written after the transition.
• Letting the migration become a forever-project: Without a defined finish line and a "last native screen" target, the mixed codebase becomes permanent and you pay both worlds' maintenance costs indefinitely.

Time and Cost: Realistic Expectations

• Brownfield pilot: One screen in production — on the order of a month.
• Mid-sized full migration (30-60 screens): 4-9 months with an incremental plan; for a full rewrite, 3-6 months to a core release plus staged scope expansion.
• What drives cost: The number of native SDKs to bridge, rebuilding the design system, test coverage, and the length of the double-maintenance window. How much existing code and logic can be reused determines the total.

The return is not one-off: one codebase means every feature ships on both platforms simultaneously, maintained by one team. For why we consider React Native the right foundation for most products, see our article on the advantages of React Native.

From the Field: Kompanse's React Native / Expo Practice

This guide reflects production practice, not theory. Our own product, Sepetteyiz, is built with React Native and Expo and is live on both the App Store and Google Play — we operate the full chain ourselves, from a single codebase through EAS builds to store compliance. We apply the same principle to client projects: discovery and dependency inventory first, then a measurable pilot, then slice-by-slice migration.

Migration Checklist

1. Screen and behavior inventory complete; usage ranked with analytics.
2. Native SDK dependencies listed; React Native/Expo equivalents verified.
3. Strategy decision (full rewrite / brownfield) made via the decision tree — and its rationale written down.
4. Performance baselines (startup, transitions, frame rate) measured on the native app.
5. Pilot screen selected; navigation, session, and theming bridges designed.
6. Turbo Module / Expo Module plan drafted for every SDK to bridge.
7. Test strategy in place: unit + contract + end-to-end; staged rollout plan ready.
8. Definition of done written: the "last native screen" target and the brownfield shell removal plan.
9. Store compliance (privacy manifest, Data Safety, account deletion) included in the migration plan.

Conclusion: Migration Is a Managed Process, Not a Leap

With proper discovery and the right strategy, migrating from native to React Native and Expo becomes an engineering process whose risk is managed screen by screen. In 2026 the toolchain — the New Architecture, Turbo Modules, Expo's brownfield support — makes that process more predictable than it has ever been. What matters is choosing the strategy that fits your app's actual condition and defining the finish line up front.

If you are weighing a migration, talk to our team — we run a live React Native product on both stores, and our mobile application development service covers discovery analysis, migration planning, and execution end to end.