Twitter • Github • MMKV Internals

This version fixes additional iOS issues with React Native 0.77+:

• Fixed nested JSI string conversion in object and array storage methods
• Resolved the "no member named 'asString' in 'facebook::jsi::String'" error
• Improved handling of JSON stringification results on iOS

This version fixes iOS compatibility with React Native 0.77+:

• Updated iOS implementation to use asString() instead of getString()
• Fixed JSON object and array handling on iOS
• Added getMultiObjectMMKV native function for iOS
• Ensures consistent API between iOS and Android for native JSON parsing

This version adds native JSON parsing for multiple items retrieval:

• Added getMultiObjectMMKV native function for parsing JSON in C++ for multiple keys at once
• Added getMultipleItemsNative and getMultipleItemsNativeAsync methods that use native parsing
• Improves performance when retrieving large collections of objects from storage
• Handles JSON parsing errors gracefully by returning the raw string when parsing fails

This version includes fixes for React Native 0.77+ compatibility:

• Fixed JSON access in native code to properly handle JSON as an object not a function
• Updated JSON.stringify and JSON.parse calls to work with newer JSI APIs
• Corrected the "getPropertyAsFunction" error when accessing JSON methods

This version includes fixes for React Native 0.77+ compatibility:

• Fixed JSI API compatibility issues by updating String handling methods
• Updated the code to work with newer JSI APIs that removed the getString() method
• Object and array serialization/deserialization now works correctly with the new JSI API

This library aims to provide a fast & reliable solution for you data storage needs in react-native apps. It uses MMKV by Tencent under the hood on Android and iOS both that is used by their WeChat app(more than 1 Billion users). Unlike other storage solutions for React Native, this library lets you store any kind of data type, in any number of database instances, with or without encryption in a very fast and efficient way. Read about it on this blog post I wrote on dev.to

Learn how to build your own module with JSI on my blog

Works only with react native 0.71.0 and above. If you are on older version of react native, keep using 0.8.x.

Starting from v0.5.0 the library has been rewritten in C++ on Android and iOS both. It employs React Native JSI making it the fastest storage option for React Native.

(~ 50K Android/30K iOS) and even smaller when packaged.

MMKV uses mmap to keep memory synced with file, and protobuf to encode/decode values to achieve best performance. You can see the benchmarks here: Android & iOS

Hooks let's the storage update your app when a change takes place in storage.

Starting from v0.5.5, thanks to the power of JSI, we now have our very own useMMKVStorage Hook. Think of it like a persisted state that will always write every change in storage and update your app UI instantly. It doesn't matter if you reload the app or restart it.

import { MMKVLoader, useMMKVStorage } from 'react-native-mmkv-storage';

const storage = new MMKVLoader().initialize();
const App = () => {
  const [user, setUser] = useMMKVStorage('user', storage, 'robert');
  const [age, setAge] = useMMKVStorage('age', storage, 24);

  return (
    <View style={styles.header}>
      <Text style={styles.headerText}>
        I am {user} and I am {age} years old.
      </Text>
    </View>
  );
};

Learn more about useMMKVStorage hook it in the docs.