Error map
useLayoutEffect SSR Warning: useLayoutEffect does nothing on the server
React · layer 1, On your device
Centre: this error. First ring: errors it is linked with (7). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (7)
Error: Hydration failed because the initial UI does not match what was rendered on the server
The HTML rendered on the server differs from the first client render, so React (Next.js/Remix) can’t attach to it.
Warning: validateDOMNesting(...): <div> cannot appear as a descendant of <p>.
The JSX produces invalid HTML nesting, which also causes hydration mismatches in SSR.
Error: Maximum update depth exceeded. This can happen when a component repeatedly calls setState inside componentWillUpdate or componentDidUpdate.
A component keeps updating itself in an effect or lifecycle — usually a useEffect that sets state its own dependencies change.
Error: Invalid hook call. Hooks can only be called inside of the body of a function component.
A hook ran outside a function component/custom hook, conditionally — or two copies of React are loaded.
Warning: useEffect must not return anything besides a function, which is used for clean-up. It looks like you wrote useEffect(async () => ...)
An async function was passed directly to useEffect, so it returns a Promise instead of a cleanup function.
Warning: Prop `className` did not match. Server: "x" Client: "y"
A prop rendered on the server differs from the client — usually CSS-in-JS class names or random IDs.
React Hook useEffect has a missing dependency (react-hooks/exhaustive-deps)
ESLint warns that the effect reads a value that isn’t in its dependency array, so it may use a stale value.
Two steps away (14)
ReferenceError: x is not defined
Code refers to a variable or function name that doesn’t exist in the current scope.
Error: Objects are not valid as a React child
You tried to render a plain object (or a Promise/Date) directly in JSX; React can only render strings, numbers, elements and arra…
Module not found: Can't resolve 'fs' (Next.js / webpack 5)
A Node.js built-in (fs, path, crypto, net) is imported into code that runs in the browser bundle.
Warning: A component is changing an uncontrolled input to be controlled
An input’s `value` started as `undefined` (uncontrolled) and later became a defined value (controlled), or vice versa.
Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...</>?
A component returns two sibling JSX elements without a single parent.
Warning: Cannot update a component (`Parent`) while rendering a different component (`Child`)
A child component updated a parent’s state during its render instead of in an effect or event handler.
Error: Too many re-renders. React limits the number of renders to prevent an infinite loop.
A state update runs during render, which triggers another render, which updates state again — forever.
Error: Actions must be plain objects. Instead, the actual type was: 'function'.
A function (thunk) was dispatched but the thunk middleware isn’t configured.
A non-serializable value was detected in the state / in an action, in the path
Redux Toolkit’s middleware found a Date, Promise, class instance or function in state or an action.
npm ERR! code ERESOLVE — unable to resolve dependency tree
npm 7+ found conflicting peer dependency requirements and refuses to install a broken tree.
AbortError: The user aborted a request. / signal is aborted without reason
A fetch was cancelled through an AbortController (or the browser cancelled it).
TypeError: Failed to execute 'json' on 'Response': body stream already read
A fetch Response body was consumed twice (e.g. calling .text() then .json()).
RuntimeError: Event loop is closed
Async code tried to use an event loop that has already been shut down.
Warning: An update to Component inside a test was not wrapped in act(...)
A component updated state after the test’s synchronous assertions — async work wasn’t awaited.
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