React's automatic batching feature optimizes performance by grouping multiple state updates within a single event into one re-render, rather than triggering a separate re-render for each state change. This reduces the number of renders and improves efficiency. Starting with React 18, automatic batching is extended to include updates in promises, setTimeout, and other asynchronous functions, not just within event handlers. This makes state management smoother and more performant, as React handles multiple updates together even in asynchronous scenarios.