React-Redux integrates with React 18 Concurrent Mode using the useSyncExternalStore hook, which eliminates the risk of UI tearing by ensuring that components always read a consistent, atomic snapshot of the Redux store state during concurrent rendering.
The integration between Redux and React's Concurrent Mode is designed to be seamless and safe, resolving a theoretical issue known as "tearing" . The cornerstone of this safe integration is the useSyncExternalStore hook, which React-Redux v8 and later versions rely on .
Tearing is a visual inconsistency where a UI component renders data from two different versions of the same state. In React's Concurrent Mode, rendering can be paused, interrupted, and resumed, which is great for performance but creates a potential problem . A component could start rendering using a 'version 1' of the state, be interrupted to allow a higher-priority update that changes the store to 'version 2', and then resume rendering. If it continued to use 'version 1' for part of its render and 'version 2' for another, the final UI would show a "torn" or inconsistent view of your application's state .
useSyncExternalStore is the official React hook designed specifically to solve the tearing problem for external stores like Redux . It acts as a dedicated bridge between React's concurrent Fiber engine and your Redux store . It works by forcing React to read the current Redux state in a single, synchronous, uninterruptible operation during the rendering process. This guarantees that every component will see a single, consistent snapshot of the state for the entire render, thereby making it immune to tearing .
React-Redux v8 and v9 are purpose-built for React 18. The integration is now seamless. For users of Redux Toolkit, the modern standard for writing Redux logic, no additional configuration is needed. When you upgrade your project to React 18 and use the corresponding React-Redux version (v8 or v9), you automatically get full, safe support for Concurrent Mode features out of the box . The tearing risk is effectively eliminated .
This foundational shift allows React-Redux v9 to drop a shim package, reducing bundle size for apps on React 18 .
The concise explanation is that
useSyncExternalStoreensures React always reads a consistent snapshot of external state, making any tearing caused by Concurrent Mode impossible .