C++ in React Native: Going Beyond JavaScript for High-Performance Mobile Apps

React Native allows developers to build mobile applications using JavaScript and React while still accessing native platform capabilities.

But what happens when JavaScript isn't enough?

What if your application needs:

• High-performance video processing
• Complex mathematical calculations
• Image or audio processing
• Cryptography
• Real-time data processing
• Cross-platform native logic
• Low-level memory control
• Native integrations that need better performance

This is where C++ can become a powerful addition to a React Native application.

C++ isn't replacing JavaScript in React Native. Instead, it can work alongside JavaScript to handle computationally intensive or performance-critical operations.

In this article, we'll understand where C++ fits into the React Native architecture, how JavaScript communicates with C++, and where this approach makes sense in real-world applications.

Why would React Native need C++?

Most React Native applications are primarily written in JavaScript or TypeScript.

A simplified architecture looks like this:

React / TypeScript
       ↓
React Native
       ↓
Native APIs
       ↓
iOS / Android

For many applications, this is more than enough.

However, JavaScript is not always the best choice for CPU-intensive workloads.

For example, imagine processing a large video frame.

A JavaScript implementation might look conceptually like:

const processedFrame = processVideoFrame(frame);

If processVideoFrame() performs millions of calculations, the JavaScript runtime can become a bottleneck.

A native implementation could instead perform the heavy processing using C++:

JavaScript
    ↓
React Native Native Layer
    ↓
  C++
    ↓
Result
    ↓
JavaScript

The important idea is:

Use JavaScript for application logic and C++ where native performance or low-level processing provides a real advantage.

Where does C++ fit into React Native?

React Native's architecture has evolved significantly over the years.

With the newer architecture, React Native provides mechanisms that make communication between JavaScript and native code more efficient.

A simplified view is:

┌──────────────────────────┐
│     React / TypeScript   │
└────────────┬─────────────┘
             │
             ▼
┌──────────────────────────┐
│    React Native / JS     │
│         Runtime          │
└────────────┬─────────────┘
             │
             ▼
┌──────────────────────────┐
│     Native Platform      │
│    iOS / Android         │
└────────────┬─────────────┘
             │
             ▼
┌──────────────────────────┐
│           C++            │
│ Performance-heavy logic  │
└──────────────────────────┘

C++ can therefore become a shared native layer that sits underneath both Android and iOS implementations.

This is particularly useful when you don't want to implement the same complex algorithm separately in:

Kotlin / Java
       +
Swift / Objective-C

Instead, you can implement the core algorithm once in C++.

Why C++ instead of Kotlin or Swift?

This is one of the most important questions.

Android has Kotlin/Java.

iOS has Swift/Objective-C.

So why introduce C++?

Because C++ can provide a shared native implementation across platforms.

For example:

                React Native
                     │
              Native Interface
                     │
             ┌───────┴───────┐
             │               │
          Android           iOS
             │               │
             └───────┬───────┘
                     │
                    C++
                     │
              Shared Algorithm

Suppose you're building a custom media-processing engine.

Without C++:

Android → Kotlin implementation
iOS → Swift implementation

With C++:

Android ──┐
          ├──→ C++ Engine
iOS ──────┘

Now the core algorithm can be shared.

This doesn't mean that the entire application should be written in C++.

Only the appropriate low-level layer should be.

Real-world use cases for C++ in React Native

There are several situations where C++ can make sense.

1. Video processing

Video is one of the most obvious examples.

Applications involving:

• Video encoding
• Video decoding
• Frame processing
• Filters
• Transcoding
• Video effects
• DRM-related processing
• Custom media pipelines

can benefit from native code.

For example:

React Native UI
      ↓
Video Player
      ↓
Native Media Layer
      ↓
C++ Processing Engine
      ↓
Decoder / Renderer

A React Native application doesn't need to understand the low-level details.

It can simply expose a high-level API:

const result = await processVideo({
  input: videoPath,
  quality: "high"
});

The heavy work can happen underneath the API.

2. Image processing

Consider an application that needs to process images locally.

For example:

Resize
Crop
Compress
Filter
Detect
Transform

Processing thousands or millions of pixels repeatedly can be computationally expensive.

C++ is well suited for this kind of workload.

A React Native API could remain simple:

const processedImage = await ImageProcessor.resize(
  image,
  1080,
  1920
);

While internally:

React Native
     ↓
Native Module
     ↓
    C++
     ↓
Image Processing

3. Cryptography

Security-sensitive applications sometimes need native cryptographic operations.

Examples include:

Encryption
Decryption
Hashing
Key derivation
Secure data processing

Instead of implementing complex cryptographic algorithms in JavaScript, applications can use well-tested native libraries.

C++ is commonly used as the underlying implementation language for many high-performance libraries.

React Native can expose only the required interface:

const encryptedData = Crypto.encrypt(data, key);

The underlying implementation can remain native.

4. Gaming and graphics

Games are another obvious use case.

A game engine typically needs:

• Physics
• Rendering
• Collision detection
• Animation
• Memory management
• Real-time calculations

These workloads can require extremely high performance.

C++ is widely used in game engines because of its performance characteristics and low-level control.

A React Native application could potentially use C++ for a specialized engine while React Native handles surrounding application UI.

5. AI and machine learning

Another interesting area is on-device AI.

Imagine:

React Native
     ↓
AI Native Module
     ↓
C++ Runtime
     ↓
ML Model
     ↓
Inference Result

The JavaScript layer could simply request:

const result = await model.predict(input);

while the native layer performs the computationally expensive inference.

This approach can be useful when inference needs to happen locally rather than sending data to a server.

6. Complex algorithms

C++ becomes especially interesting when your application contains algorithms that are computationally expensive.

For example:

• Large data processing
• Graph algorithms
• Signal processing
• Compression
• Search algorithms
• Parsing
• Computer vision
• Mathematical calculations

Instead of repeatedly executing expensive calculations in JavaScript, the core algorithm can be implemented in C++.

JavaScript → C++ communication

This is where things become technically interesting.

The JavaScript application needs a way to communicate with the native implementation.

Conceptually:

JavaScript
    │
    │ Function Call
    ▼
Native Interface
    │
    ▼
   C++
    │
    │ Result
    ▼
JavaScript

For example:

const result = NativeCalculator.calculate(1000000);

The native implementation might eventually call:

double calculate(double input) {
// Heavy calculation
}

The JavaScript developer doesn't need to know how the calculation works.

They only need to know the API contract.

What is JSI?

If you're serious about understanding C++ in modern React Native, JSI (JavaScript Interface) is an important concept.

JSI provides a lower-level interface between JavaScript and native code.

Historically, React Native applications relied heavily on asynchronous communication through the bridge.

Conceptually:

JavaScript
     ↓
   Bridge
     ↓
  Native

The newer architecture provides a different approach.

JSI allows native code to interact more directly with the JavaScript runtime.

Conceptually:

JavaScript Runtime
       ↕
      JSI
       ↕
   Native / C++

This can reduce some of the overhead associated with traditional bridge-based communication.

Why JSI matters for C++

JSI itself is implemented around C++ concepts and provides a foundation for creating high-performance native integrations.

This makes C++ particularly interesting for React Native developers who want to work closer to the runtime.

For example, a native C++ implementation can expose functionality that JavaScript can call.

Conceptually:

jsi::Value calculate(
    jsi::Runtime& runtime,
    const jsi::Value* args,
    size_t count
) {
    // C++ implementation
}

The JavaScript side could then interact with the exposed function.

The exact implementation depends on the React Native architecture and the native module design, but the important concept is the same:

JS
 ↓
JSI
 ↓
C++

TurboModules and C++

Modern React Native also introduces TurboModules as part of the New Architecture.

TurboModules provide a more efficient native module system and work with React Native's code-generation approach.

A simplified architecture looks like:

TypeScript Specification
          ↓
      Codegen
          ↓
   Native Interface
          ↓
      C++ / Native

This is particularly interesting because it allows React Native developers to define a typed contract while implementing performance-critical logic in native code.

For example, a TypeScript specification could conceptually define:

interface VideoProcessor {
processVideo(path: string): Promise<string>;
}

The underlying implementation can then be handled natively.

This creates a clean separation:

Business/UI Logic
       ↓
TypeScript
       ↓
Native Contract
       ↓
C++ Implementation

Fabric and C++

C++ also becomes relevant when looking at Fabric, React Native's newer rendering system.

Fabric moves more of the rendering infrastructure toward C++ and provides a common core across platforms.

A simplified architecture is:

React
↓
Shadow Tree
↓
Fabric
↓
C++
↓
Platform Renderer

This is one reason modern React Native developers can benefit from understanding C++.

You don't necessarily need to become a C++ expert to build React Native applications.

But understanding:

• pointers
• references
• memory management
• classes
• templates
• RAII
• smart pointers
• threading
• native interfaces

can make the architecture much easier to understand.

C++ and React Native are not competitors

It's important not to think about this as:

JavaScript OR C++

Instead, think:

JavaScript
    +
TypeScript
    +
Native APIs
    +
   C++

Each layer has a different responsibility.

A practical architecture might look like:

┌─────────────────────────────┐
│       React / TypeScript    │
│       UI + Business Logic   │
└──────────────┬──────────────┘
               │
┌──────────────▼──────────────┐
│      React Native Layer     │
│  Components + Native APIs   │
└──────────────┬──────────────┘
               │
┌──────────────▼──────────────┐
│       Native Platform       │
│    Android / iOS Layer      │
└──────────────┬──────────────┘
               │
┌──────────────▼──────────────┐
│             C++             │
│   Performance-heavy logic   │
└─────────────────────────────┘

When should you NOT use C++?

This is just as important as understanding where C++ helps.

Don't introduce C++ simply because it is faster.

For a normal React Native application containing:

• Forms
• API calls
• Navigation
• Authentication
• Lists
• Basic animations
• Business logic
• Standard UI components

C++ is usually unnecessary.

For example, there is no reason to implement:

const fullName =${firstName} ${lastName};

in C++.

That would add complexity without providing meaningful benefits.

The goal should be:

Use C++ only when its advantages justify the additional complexity.

The cost of introducing C++

C++ isn't free from an engineering perspective.

Once you introduce a native C++ layer, you may need to deal with:

Memory management

You need to understand:

• Pointers
• References
• Ownership
• Smart pointers
• Object lifetime
• Threading

You may need to manage:

• Worker threads
• Synchronization
• Race conditions
• Deadlocks
• Thread safety
• Build systems

You may encounter:

• CMake
• NDK
• Xcode
• Clang
• Gradle
• CocoaPods
• Debugging

Debugging a crash can become more complicated:

JavaScript
   ↓
React Native
   ↓
Native
   ↓
  C++
   ↓
Segmentation fault

Now you need native debugging skills.

C++ can also improve your React Native career

This is an underrated benefit.

React Native developers who understand native development can work on a much broader range of problems.

Instead of being limited to:

• React
• JavaScript
• TypeScript

you can move toward:

React Native
     ↓
Android / iOS
     ↓
    C++
     ↓
    JSI
     ↓
   Fabric
     ↓
TurboModules
     ↓
Native Performance

This opens doors toward roles involving:

• Mobile infrastructure
• React Native platform engineering
• Media SDKs
• Video infrastructure
• Performance engineering
• Native SDK development
• C++ mobile development
• Cross-platform frameworks

A practical learning roadmap

If you're already an experienced React Native developer, I wouldn't recommend starting with an enormous C++ course.

Instead, learn C++ specifically from a React Native native-development perspective.

Phase 1 — C++ fundamentals

Learn:

• Variables
• Functions
• Classes
• Objects
• Constructors
• Destructors
• Pointers
• References
• const
• STL
• Vectors
• Maps
• Strings
• Templates

Phase 2 — Memory management

Focus heavily on:

• Stack vs Heap
• Pointers
• References
• RAII
• unique_ptr
• shared_ptr
• weak_ptr
• Move semantics

These concepts become extremely useful when working with native code.

Phase 3 — Modern C++

Learn:

C++11
C++14
C++17
C++20 basics

Especially:

• auto
• lambda functions
• smart pointers
• move semantics
• range-based loops
• optional
• variant

Phase 4 — Android NDK

Then move into Android native development.

Learn:

• Android NDK
• CMake
• JNI
• C++
• Native libraries

Architecture:

React Native
      ↓
   Android
      ↓
     JNI
      ↓
     C++

Phase 5 — iOS native integration

Understand:

• Objective-C++
• Swift ↔ Objective-C++
• C++ libraries
• Xcode
• CocoaPods

You don't necessarily need to become a Swift expert.

Your goal is to understand how the C++ layer can be integrated into the iOS application.

Phase 6 — React Native internals

This is where your existing React Native experience becomes extremely valuable.

Learn:

• JSI
• TurboModules
• Codegen
• Fabric
• Bridgeless Mode
• Hermes
• New Architecture

Then start reading actual React Native source code.

At this point, you'll start seeing why React Native uses C++ internally.

Final thoughts

C++ doesn't make every React Native application faster.

It makes sense when you have a problem that benefits from:

• High computational performance
• Low-level control
• Native memory management
• Cross-platform native logic
• Existing C/C++ libraries
• Heavy media or graphics processing

For experienced React Native developers, learning C++ is therefore less about abandoning JavaScript and more about understanding what happens underneath React Native.

The most powerful combination isn't:

React Native vs C++

It's:

React Native + Native Development + C++

Once you understand all three layers, you can move from building React Native applications to building native-powered React Native systems.

And that's a very different level of engineering.

Conclusion

If you're already comfortable with React Native, you don't need to become a C++ specialist overnight.

Start small.

Learn modern C++.

Understand memory management.

Build a native module.

Learn JSI.

Understand TurboModules and Fabric.

Then gradually move into the React Native internals.

The goal isn't to write your entire React Native application in C++.

The goal is to know when JavaScript is the right tool—and when it isn't.