Fix memory leaks and cleanup warnings in React
Memory leaks in React occur when subscriptions, timers, or async operations continue running after a component unmounts. This causes performance degradation and the classic 'can't perform a state update on an unmounted component' warning.
Error messages you might see
Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application.AbortError: The operation was aborted.Why this happens in AI-generated code
Missing cleanup in useEffect
AI-generated code sets up intervals, event listeners, or WebSocket connections in useEffect without returning a cleanup function to tear them down on unmount.
Unaborted fetch requests
AI tools generate useEffect data fetching without AbortController, so responses arrive after the component unmounts and try to call setState on a dead component.
Global event listeners not removed
AI-generated code adds window or document event listeners during component mount but never removes them, accumulating listeners across navigations.
How to fix it
Return cleanup functions from useEffect
Every useEffect that creates a subscription, timer, or listener should return a function that cleans it up: clearInterval, removeEventListener, unsubscribe, or abort.
Use AbortController for fetch requests
Create an AbortController in useEffect, pass its signal to fetch, and call controller.abort() in the cleanup function to cancel pending requests on unmount.
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Frequently asked questions
How do I detect memory leaks in React?
Use Chrome DevTools Memory tab to take heap snapshots before and after navigating. Compare them to find detached DOM elements and growing object counts. React DevTools can also show component mount/unmount patterns.
Is the 'unmounted component' warning always a memory leak?
It indicates a potential leak — an async operation completed after unmount. While React 18 removed this warning, the underlying issue still wastes resources. Always clean up async work.
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