React Native 0.84 and Expo SDK 55: why existing apps no longer need a full rebuild
React Native 0.84 made the Hermes V1 engine the default and Expo SDK 55 added brownfield support, letting teams migrate an existing native app screen by screen. Reported code sharing is 80–95%.
5 October 2026
The cross-platform question used to be framed as a rebuild: throw away the native apps, start again in React Native or Flutter. React Native 0.84 (February 2026) and Expo SDK 55 change that framing. Hermes V1 is now the default JavaScript engine, bringing faster execution and lower memory use, and the New Architecture, mandatory since 0.82 in October 2025, is fully settled.
The more important change for buyers is brownfield support. Teams can now add React Native screens to an existing iOS or Android app one at a time, rather than replacing everything in one go. Reported results are 80–95% code sharing between platforms and 20–40% faster feature delivery.
Why this matters commercially
A full rewrite means a long period with no new features, a large upfront bill and a risky switch-over. A screen-by-screen migration lets you start with the part of the product that changes most, often onboarding, settings or a checkout flow, and prove the saving before committing further. Native code stays where it earns its keep: camera, payments and performance-critical screens.
Flutter remains a strong alternative, holding an estimated 46% of cross-platform market share against React Native’s 35%. But for companies already running separate native apps, an incremental path is often the lower-risk choice.
Questions to ask your developer
- Which screens would move first, and what would we measure?
- How much shared code do you realistically expect for our product?
- What is the plan if we stop halfway?
So what
If you are paying twice for every feature on iOS and Android, you probably do not need a rewrite, but you do need a migration plan. BuildApps builds and migrates across iOS, Android and cross-platform projects. To scope a phased move, start a project.