Error map
Adjacent JSX elements Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...</>?
React · layer 1, On your device
Centre: this error. First ring: errors it is linked with (12). 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 (12)
Warning: Functions are not valid as a React child. This may happen if you return a Component instead of <Component /> from render.
A function (usually a component itself) was rendered instead of calling/rendering it as an element.
Error: useNavigate() may be used only in the context of a <Router> component.
A React Router hook ran in a component that isn’t rendered inside a Router provider.
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…
Dockerfile parse error line N: unknown instruction
A line in the Dockerfile doesn’t start with a valid instruction — usually a broken line continuation or a typo.
SyntaxError: Invalid regular expression: /x/: Unterminated group
A regex pattern has invalid syntax — unbalanced parentheses/brackets or unescaped special characters.
Error: Nothing was returned from render. This usually means a return statement is missing.
A component returned undefined (React 17 and earlier) — usually a missing return or a return followed by a line break.
Error: No QueryClient set, use QueryClientProvider to set one
TanStack Query hooks ran outside a QueryClientProvider (or a duplicate copy of the library is installed).
ReferenceError: React is not defined / 'React' must be in scope when using JSX
JSX was compiled with the classic runtime, which needs React imported in every file.
Warning: Received `true` for a non-boolean attribute `x`.
A boolean was passed to a DOM attribute that expects a string, or a custom prop leaked through to a DOM element.
Warning: validateDOMNesting(...): <div> cannot appear as a descendant of <p>.
The JSX produces invalid HTML nesting, which also causes hydration mismatches in SSR.
Warning: Function components cannot be given refs. Attempts to access this ref will fail. Did you mean to use React.forwardRef()?
A ref was passed to a function component that doesn’t forward it.
Error: Minified React error #31; visit https://react.dev/errors/31 for the full message
A production React build threw an error whose message was shortened to a number.
Two steps away (30)
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.
Warning: Each child in a list should have a unique "key" prop
When rendering a list with `.map()`, each element needs a stable, unique `key` so React can track items between renders.
Error: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined
JSX referenced a component that is undefined — almost always a default/named import mismatch.
RuntimeError: Working outside of application context.
Code used current_app, g, or a Flask extension (like SQLAlchemy) without an active Flask application context.
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.
No routes matched location "/x"
React Router found no route definition for the current URL.
TypeError: Cannot read properties of undefined (reading 'x')
You tried to access a property on a value that is `undefined` (or `null`) — usually data that hasn’t loaded yet or a wrong proper…
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: Invalid DOM property `class`. Did you mean `className`?
HTML attribute names were used in JSX instead of their React/DOM property names.
PHP Parse error: syntax error, unexpected …
PHP can’t parse the file because of a syntax mistake — the real error is often on the line before the one reported.
IndentationError: unexpected indent / expected an indented block
Python’s block structure is broken — inconsistent indentation or mixed tabs and spaces.
npm ERR! code ELIFECYCLE / Command failed with exit code 1
An npm script (build, start, test, postinstall) exited with an error. ELIFECYCLE is only the wrapper — the real error is printed…
SyntaxError: Unexpected token '<' (HTML served instead of JavaScript)
The browser loaded a .js file but received HTML (an error page or the SPA index.html).
SyntaxError: Unexpected end of input
The parser reached the end of the code (or JSON) while still expecting more — a missing } ) ] or empty JSON.
SyntaxError: missing ) after argument list
A function call’s parentheses are unbalanced — often an unescaped quote or a missing comma/plus.
Error: A component suspended while responding to synchronous input.
A component suspended (lazy load or data fetch) during an update that wasn’t wrapped in a transition, and there is no Suspense bo…
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.
TypeError: Cannot destructure property 'user' of 'useContext(...)' as it is undefined.
A component read a context with no matching Provider above it.
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.
ReferenceError: x is not defined
Code refers to a variable or function name that doesn’t exist in the current scope.
API Error: Invalid or unsupported API version
The API version you requested — in the URL, a header or the SDK config — doesn’t exist or has been retired.
API Error: Feature not enabled for this account (feature_not_enabled / not available on your plan)
The endpoint or option exists, but your account, plan, region or project hasn’t been granted access to it.
Warning: `key` is not a prop. Trying to access it will result in `undefined` being returned.
A component tried to read props.key, which React reserves and never passes down.
Vue: [Vue warn]: Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders
A child component assigned to a prop. Props flow one way — the parent owns the value.
Warning: useLayoutEffect does nothing on the server
A component using useLayoutEffect was server-rendered, where layout effects can’t run.
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.
error: cannot lock ref 'refs/remotes/origin/x': is at … but expected … / unable to update local ref
Git couldn’t update a reference — stale remote-tracking refs, case-only branch name clashes, or a leftover lock file.
warning: ignoring broken ref refs/remotes/origin/HEAD
A ref file is empty or points to a missing object — usually refs/remotes/origin/HEAD after the default branch changed.
Warning: componentWillMount has been renamed, and is not recommended for use.
A class component uses legacy lifecycle methods (componentWillMount/WillReceiveProps/WillUpdate).
Error: A cross-origin error was thrown. React doesn't have access to the actual error object in development.
An error happened in a script loaded from another origin, so the browser hid the details from React.
Map another error
Popular: 4035004000xC000007BTypeErrorCritical error404NullPointerException