Why React production errors are different
React errors in production are often different from errors in development. React's strict mode catches additional issues in dev, and production builds are minified, making stack traces harder to read without source maps.
1. Cannot read properties of undefined
Most common React production error. Usually means you're rendering before data has loaded. Fix: conditional rendering with loading states, or optional chaining (data?.field).
2. Maximum update depth exceeded
Infinite re-render loop. Usually caused by updating state inside useEffect without proper dependency array. Fix: audit your useEffect dependencies.
3. Warning: Each child in a list should have a unique "key" prop
Not an error in production, but causes performance issues and incorrect rendering after list updates. Fix: always use stable, unique IDs as keys (never array index for dynamic lists).
4. Cannot update a component while rendering a different component
State update triggered during render of another component. Common in complex state management setups. Fix: move the state update to useEffect.
5. Hydration failed
Server and client rendered different content in Next.js/Remix. Causes silent UI inconsistencies. Common culprit: browser-only APIs (window, localStorage) used during SSR.
6. Objects are not valid as a React child
Trying to render a JavaScript object directly in JSX. Usually means you forgot to access a property: {user} instead of {user.name}.
7. Too many re-renders
State update in render causing infinite loop. Fix: move state updates into event handlers or useEffect, never call setState unconditionally in the render body.
8. useEffect cleanup not working
Memory leaks from subscriptions, timers, or event listeners not cleaned up. In production this manifests as memory growth and eventual crashes.
9. Context value changed on every render
Passing a new object literal as Context value causes all consumers to re-render. Fix: memoize the context value.
10. Promise rejection unhandled in event handler
Async event handlers that throw don't propagate to error boundaries. These are silent failures. Fix: add try/catch to all async event handlers.
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