react-native-nitro-base64 ⚡

The fastest Base64 library for React Native — powered by simdutf SIMD C++ and Nitro Modules.

Processes a 1.3MB image 26x faster than atob/btoa and 1.8x faster than react-native-quick-base64.

| iPhone | Android | | --- | --- | | | |

🤔 Why this library?

Most React Native base64 libraries hit the same bottlenecks:

• 🐢 Pure JS (base64-js) — slow. No native acceleration.
• ⚠️ atob/btoa — fast for tiny strings, falls apart on binary data at scale.
• ⚠️ String-based native — crosses the JSI bridge as UTF-16, doubling memory for binary payloads.

react-native-nitro-base64 uses SIMD instructions (AVX-512 on x86, NEON on Apple Silicon) to process 64 bytes per CPU instruction, and exposes ArrayBuffer/Uint8Array APIs that bypass string marshaling entirely.

📊 Benchmark — 30 iterations, iPhone (Apple Silicon)

Tested against [email protected]

Small image (7KB)

| Library | Time | vs. nitro-base64 | |---|---|---| | ⚡ nitro-base64 decodeBuffer / fromByteArray | 0.06ms | — | | react-native-quick-base64 | 0.11ms | 1.8x slower | | atob / btoa (Hermes) | 1.04ms | 17x slower |

Large image (1.3MB)

| Library | Time | vs. nitro-base64 | |---|---|---| | ⚡ nitro-base64 decodeBuffer / fromByteArray | 7.5ms | — | | react-native-quick-base64 | 13.6ms | 1.8x slower | | atob / btoa (Hermes) | 203ms | 26x slower |

📦 Installation

yarn add react-native-nitro-base64
yarn add react-native-nitro-modules

Then follow Nitro's setup guide for autolinking.

🔧 Setup

Call install() once before your app mounts:

// index.js
import { install } from 'react-native-nitro-base64';
import { AppRegistry } from 'react-native';
import App from './src/App';
import { name as appName } from './app.json';

install();
AppRegistry.registerComponent(appName, () => App);

📖 API

| Function | Input → Output | Notes | |---|---|---| | encode(str, urlSafe?) | string → base64 string | URL-safe optional | | decode(base64) | base64 string → string | Auto-detects standard & URL-safe | | encodeBuffer(ArrayBuffer, urlSafe?) | ArrayBuffer → base64 string | 🚀 Zero-copy, fastest for images | | decodeBuffer(base64) | base64 string → ArrayBuffer | 🚀 Zero-copy, fastest for images | | fromByteArray(Uint8Array, urlSafe?) | Uint8Array → base64 string | Drop-in for react-native-quick-base64 | | toByteArray(base64) | base64 string → Uint8Array | Drop-in for react-native-quick-base64 |

🚀 Usage

🖼️ Images & files — encodeBuffer / decodeBuffer

Images are binary data. Sending binary through a JS string crosses the JSI bridge as UTF-16, doubling memory. ArrayBuffer skips that entirely — raw bytes go straight to C++.

import { encodeBuffer, decodeBuffer } from 'react-native-nitro-base64';

// Upload image to API
const response = await fetch(imageUri);
const buffer = await response.arrayBuffer();
const base64 = encodeBuffer(buffer); // → "iVBORw0KGgo..."

// Decode API response for <Image> component
const buffer = decodeBuffer(base64String); // → ArrayBuffer

🔑 Text & JWT — encode / decode

import { encode, decode } from 'react-native-nitro-base64';

const encoded = encode('Hello World!');  // "SGVsbG8gV29ybGQh"
const decoded = decode(encoded);         // "Hello World!"

// URL-safe for JWT / URL params
const token = encode(payload, true);

🔐 Web Crypto & hashing — fromByteArray / toByteArray

Drop-in replacement for react-native-quick-base64. Same API, faster engine.

import { fromByteArray, toByteArray } from 'react-native-nitro-base64';

// SHA-256 hash → base64
const hash = new Uint8Array(await crypto.subtle.digest('SHA-256', data));
const encoded = fromByteArray(hash);

// base64 → text
const bytes = toByteArray(base64String);
const text = new TextDecoder().decode(bytes);

📱 Platform Support

| Platform | Engine | |---|---| | iOS | C++ (simdutf, NEON SIMD) | | Android | C++ (simdutf, NEON / AVX2 SIMD) |

📄 License

MIT

🙏 Credits

• simdutf — SIMD-accelerated Unicode & Base64
• Nitro Modules — JSI native module framework