Open-Source Databases · mrousavy

react-native-mmkv

react-native-mmkv is a key-value storage library for React Native that claims ~30x faster performance than AsyncStorage by using native C++ bindings. It supports encryption, multiple instances, and works on iOS, Android, and Web.

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Source: GitHub — github.com/mrousavy/react-native-mmkv

8.4k

GitHub stars

339

Forks

TypeScript

Primary language

MIT

License (OSI-approved)

Key facts

Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.

Field	Value
Repository	mrousavy/react-native-mmkv
Owner	mrousavy
Primary language	TypeScript
License	MIT — OSI-approved
Stars	8.4k
Forks	339
Open issues	18
Latest release	v4.3.2 (2026-06-22)
Last updated	2026-06-29
Source	https://github.com/mrousavy/react-native-mmkv

What react-native-mmkv is

A React Native wrapper around Tencent's MMKV C++ library using JSI and Nitro modules for synchronous key-value operations. Supports AES-128/256 encryption, multiple storage instances, ArrayBuffer serialization, and custom storage paths.

Quickstart

Get the react-native-mmkv source

Clone the repository and explore it locally.

terminalbash

1git clone https://github.com/mrousavy/react-native-mmkv.git2cd react-native-mmkv3# follow the project's README for install & configuration

Need it deployed, integrated, or customized instead? DEV.co ships production installs.

Best use cases

High-frequency local data caching

Apps requiring frequent synchronous reads/writes of user preferences, session tokens, or frequently-accessed configuration without async overhead.

Multi-user or multi-tenant mobile apps

Applications needing isolated storage instances per user (e.g., user-specific settings) while sharing a global app storage namespace.

Encrypted sensitive data storage

Mobile apps storing PII, authentication tokens, or other sensitive data requiring on-device AES encryption without external server dependency.

Implementation considerations

V4 is a Nitro module requiring compatibility verification with your React Native and Nitro versions; migration path from V3 is non-trivial.
Synchronous API can block the JS thread if called in tight loops; monitor performance impact on UI responsiveness in hot paths.
Encryption keys must be managed securely (not hardcoded); consider integration with platform-specific secure storage (Keychain/Keystore) for key material.
Multiple instance isolation is instance-ID based; ensure consistent ID usage across app lifecycle to avoid data fragmentation.
Custom storage paths and App Group configurations require platform-specific setup (Info.plist for iOS, manifest for Android).

When to avoid it — and what to weigh

Large dataset persistence — MMKV is optimized for key-value pairs; complex relational data or large document stores should use SQLite or similar databases.
Async-first architecture required — Apps with strict async/await patterns and no tolerance for synchronous calls may face architectural conflicts with MMKV's sync-only API.
Web-primary development — While Web support exists, performance advantages are native-platform specific; Web-only apps should evaluate conventional storage solutions.
Legacy React Native projects — V4 migration to Nitro modules may conflict with older bridging architectures; V3 compatibility needs assessment.

License & commercial use

Licensed under MIT (Massachusetts Institute of Technology License), a permissive open-source license. Permits commercial use, modification, and distribution with attribution.

MIT license explicitly permits commercial use and modification. No license restrictions on proprietary app distribution. However, audit your dependency chain for any MMKV C++ library (Tencent/MMKV) license terms independently; this wrapper's license does not supersede upstream dependencies.

DEV.co evaluation signals

Editorial assessment — not user reviews. Directional, with an explicit confidence level.

Signal	Assessment
Maintenance	Active
Documentation	Strong
License clarity	Clear
Deployment complexity	Low
DEV.co fit	Good
Assessment confidence	High

Security considerations

Encryption support (AES-128/256) relies on Tencent's MMKV C++ implementation; no independent security audit data provided. Synchronous API means no async/await cleanup guarantees on exception. Encryption keys are developer-managed (no HSM or platform keychain integration documented). Multi-process mode (App Groups) increases attack surface if data is read by untrusted extensions. Local file permissions depend on OS sandbox; no additional app-level access control.

Alternatives to consider

AsyncStorage (React Native built-in)

Familiar, no native module setup required, but significantly slower (~30x per library claims); suitable for non-performance-critical apps.

WatermelonDB

Full relational database for React Native with offline-first sync; better for complex schemas, but heavier than key-value storage.

Expo SecureStore / React Native Secure Storage

Native encryption via platform Keychain/Keystore for small sensitive data; simpler API but not optimized for bulk key-value reads.

Software development agency

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Contact our engineering team to assess MMKV's fit for your React Native architecture, migration strategy, and security requirements.

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Related open-source tools

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react-native-mmkv-storage sdk-for-react-native react-native-testing-library

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react-native-mmkv FAQ

How much faster is MMKV than AsyncStorage?

Per the library's StorageBenchmark, ~30x faster for repeated get operations on iPhone 11 Pro. Actual speedup depends on data size and workload pattern.

Can I use MMKV in Expo managed workflow?

Yes, via `npx expo install` and `npx expo prebuild`, but you exit managed workflow for custom native builds. Pre-built Expo Go does not support native modules.

Is data encrypted by default?

No. By default, MMKV stores key-values in plain text, relying on OS-level file sandbox. Encryption is opt-in via `encryptionKey` parameter or `encrypt()` method.

Can I migrate from AsyncStorage to MMKV?

Manual migration required; read all AsyncStorage keys, then write to MMKV instance. No automatic tooling provided.

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