React Error Boundaries catch errors that occur while React renders a descendant component. They do not generally catch exceptions from event handlers, timer callbacks, or other asynchronous work, because those errors happen outside the render work the boundary observes. Handle interaction and ordinary async failures in the code that runs them; use a boundary for render failures. React documents narrow exceptions, including rejected Promises read with use and errors thrown inside the startTransition function returned by useTransition.
What an Error Boundary catches—and what it does not
An Error Boundary protects a region of rendered UI. When a descendant throws during rendering, React can show the boundary’s fallback in place of the failed region. The boundary’s scope is not every callback or operation associated with components beneath it.
React’s Component reference lists event handlers and asynchronous callbacks such as setTimeout and requestAnimationFrame among the errors boundaries do not catch. It also lists server-rendering errors and errors thrown by the boundary itself. The documented exception relevant to asynchronous work is an error thrown inside the function passed to startTransition from useTransition.
| Where the failure occurs | What handles it | Practical response |
|---|---|---|
| Descendant render | Error Boundary | Show fallback UI; optionally report the error and component stack. |
| Event handler | Handler logic | Catch expected exceptions or Promise rejections and update application state. |
| Timer or animation callback | Callback logic | Handle the failure in the callback or explicitly move it into application state. |
Promise read with use |
Suspense while pending; Error Boundary if rejected | Reuse a cached Promise instance and provide appropriate loading and error UI. |
| Data fetched in an Effect or event handler | Not detected by Suspense | Manage loading and failure in the fetch flow and application state. |
Function passed to startTransition from useTransition |
Error Boundary, in React’s documented exception | Use this as a specific exception, not a general rule for asynchronous callbacks. |
Why event-handler errors need their own handling
An event handler runs because of an interaction, not because React is rendering the descendant tree. Declaring the handler in a component inside a boundary does not make exceptions from that handler part of the boundary’s render-error handling.
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Catch expected failures where the interaction occurs, then represent the outcome in the UI. For example:
async function handleSave() {
try {
await saveRecord();
setStatus('saved');
} catch (error) {
setStatus('failed');
}
}This gives the application a chance to show local feedback—for example, a failure message beside a form—rather than relying on a boundary that will not receive the handler’s exception. React’s guidance is to reserve Error Boundaries for errors they can handle during rendering.
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Why timers and ordinary async work are outside the boundary
A callback scheduled with setTimeout or requestAnimationFrame runs later, after the render work that created or scheduled it. Its exception is not automatically delivered to a surrounding Error Boundary. Handle it within the callback, or catch a rejected Promise where that Promise is used. If a failure should replace a larger rendered region with a boundary fallback, explicitly translate the failure into application state that causes a render-time error; do not assume the original callback exception will do this.
Suspense does not automatically handle data fetched in an Effect or event handler. Those fetch flows need their own loading and failure handling. Suspense and Error Boundaries work together in a different, render-integrated case: a component reads a Promise with React’s use API.
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How Promise errors work with use and Suspense
When a component reads a pending Promise with use, React suspends rendering and the nearest <Suspense> boundary can show its loading fallback. If that Promise rejects, React sends the rejection to the nearest Error Boundary. This is not the same as fetching in an Effect or catching a rejection in an event handler.
The Promise passed to use must be cached so the same instance is reused across renders. For retry behavior, React’s use reference describes producing a replacement Promise and resetting the boundary, including through reset keys or a transition. Do not wrap use in try/catch: suspension is part of React’s rendering control flow, and catching it can lead to incorrect behavior.
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Why try/catch around JSX does not catch a child render error
This parent does not catch an error thrown later while React renders Child:
function Parent() {
try {
return <Child />;
} catch (error) {
return <p>Could not render child</p>;
}
}Returning a JSX element does not synchronously render its child inside the JavaScript try block. React’s error-boundaries lint documentation explains that try/catch cannot catch errors that happen during React’s rendering process; render errors bubble through the component tree. Use an Error Boundary around the region whose render failure should be replaced with fallback UI.
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What belongs in an Error Boundary
A class Error Boundary uses static getDerivedStateFromError to update state so it can render a fallback. It may use componentDidCatch to report the error and component stack to an error-reporting service. A simplified implementation is:
class ErrorBoundary extends React.Component {
state = { hasError: false };
static getDerivedStateFromError(error) {
return { hasError: true };
}
componentDidCatch(error, info) {
reportError(error, info.componentStack);
}
render() {
if (this.state.hasError) return this.props.fallback;
return this.props.children;
}
}React’s current Component reference describes this class-based pattern and says there is no direct function-component equivalent for componentDidCatch yet; its guidance is to reuse a boundary component or use a package that implements one. Choose boundaries around UI regions that should fail together rather than wrapping every component individually.
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