Cross-Platform App Development — UK
One codebase
or two?
Make the right call.
Wall & Fifth is a London cross-platform app development studio building iOS and Android products with React Native and Expo. We help decide what should be shared, what should stay platform-specific, and whether cross-platform is actually the right architecture for the product.
The architecture decision
Cross-platform is not “write once and forget about the platforms.”
Share what should be shared
Core product logic, API integration, state, navigation and much of the interface can often live in one maintained application codebase.
Split what should be different
iOS and Android do not need to behave identically. Platform-specific UI, permissions and device behaviour can diverge where that improves the product.
Choose architecture deliberately
The goal is not maximum code sharing at any cost. The goal is the simplest maintainable architecture that delivers the right product on both platforms.
Shared vs specific
What actually
gets shared?
A serious cross-platform build is usually a shared product core with deliberate platform-specific edges.
The honest comparison
When cross-platform wins.
And when native should win instead.
React Native + Expo
The stack we use
for cross-platform.
React Native allows application interfaces and product logic to be written in React and TypeScript while integrating with native iOS and Android capabilities where required.
Expo provides tooling around development, builds, updates and access to common device capabilities. Together they provide a practical production stack for many modern mobile products.
We still treat the underlying platforms as platforms. A cross-platform architecture should reduce unnecessary duplication, not pretend iOS and Android are identical.
TypeScript
Shared product logic and application code.
React Native
Mobile interface and application architecture.
Native APIs
Platform capabilities integrated where required.
Two stores
Separate production builds from one product codebase.
The long-term difference
The biggest saving is not just the first build.
One core feature change
A product feature can often be implemented once in the shared application layer instead of being independently recreated in two unrelated projects.
One architecture to understand
A smaller surface area makes onboarding, debugging and continued product development simpler for the team maintaining the app.
Platform differences stay explicit
Where iOS and Android genuinely need different implementations, those differences can still be isolated and maintained deliberately.
Pricing
Price the product,
not the number of platforms.
A defined production mobile product with a shared React Native codebase and the core functionality required for launch.
A larger system with richer workflows, multiple user types, integrations, backend tooling or broader release requirements.
Common questions
Before you choose the architecture.
Related expertise
Go deeper on the platform or the stack.
Choose the architecture
before you pay to build it.
We'll tell you whether cross-platform makes sense for the product, what should be shared, and where platform-specific work is actually justified.
Book a scoping call