Error map

Invalid <Link> with <a> child. Please remove <a> Next.js 13+: Error: Invalid <Link> with <a> child. Please remove <a> or use <Link legacyBehavior>

Next.js · 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.

1 · On your device 4 · Application & API 7 · Build & delivery

Directly related (7)

Hydration failedReact

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.

CORS error calling Next.js API route / route handlerNext.js

Browser: Access to fetch at 'https://api.example.com/api/data' from origin 'https://app.example.com' has been blocked by CORS policy (Next.js route handler)

A cross-origin request to your Next.js API route is blocked because the response lacks CORS headers.

Conflicting app and page file was foundNext.js

Next.js: ⨯ Conflicting app and page file was found, please remove the conflicting files to continue: "pages/index.tsx" - "app/page.tsx"

The same URL is defined in both the `app` and `pages` directories.

Failed prop type: The prop href expects a string or object in <Link>Next.js

Next.js: Error: Failed prop type: The prop `href` expects a `string` or `object` in `<Link>`, but got `undefined` instead

`` received `undefined` (or another invalid value), so Next.js can't build the link.

You have a Server Component that imports next/router. Use next/navigation insteadNext.js

Next.js: You have a Server Component that imports next/router. Use next/navigation instead

`next/router` (Pages Router) was imported in an App Router component.

next build: JavaScript heap out of memoryNext.js

Next.js: FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory (during next build)

Node ran out of memory while building a large Next.js app (or on a small CI/Vercel runner).

next build: fetch failed ECONNREFUSED (build-time API)Next.js

Next.js: Error occurred prerendering page "/blog" TypeError: fetch failed { cause: Error: connect ECONNREFUSED 127.0.0.1:3000 }

During `next build` a page tried to fetch data from a server (often your own app or an API) that isn't running yet.

Two steps away (21)

ReferenceErrorJavaScript

ReferenceError: x is not defined

Code refers to a variable or function name that doesn’t exist in the current scope.

Objects are not valid as a React childReact

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…

Invalid hook callReact

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.

CORS blocked (Laravel API)Laravel

Browser: Access to XMLHttpRequest at 'https://api.example.com' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header — Laravel

The browser blocked a cross-origin call to your Laravel API because the response lacks the right CORS headers.

Hydration error: <div> cannot be a descendant of <p>Next.js

Next.js: Warning: validateDOMNesting(...): <div> cannot appear as a descendant of <p> / In HTML, <p> cannot be a descendant of <p>. This will cause a hydration error

The rendered HTML has an invalid element nesting, so the browser "fixes" it and React's hydration no longer matches.

createContext only works in Client ComponentsNext.js

Next.js: You're importing a component that needs createContext. It only works in a Client Component but none of its parents are marked with "use client"

A context provider (or a lib that uses `createContext`) is used in a Server Component.

path-to-regexpNode.js

TypeError: Missing parameter name at 1 (path-to-regexp)

An Express 5 (path-to-regexp v8) route uses old wildcard syntax like '*' or '/:id?'.

No routes matchedReact

No routes matched location "/x"

React Router found no route definition for the current URL.

Prerender errorReact

Error occurred prerendering page "/x". Read more: https://nextjs.org/docs/messages/prerender-error

A page threw an error while Next.js was rendering it at build time.

non-boolean attributeReact

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.

needs useStateReact

You're importing a component that needs useState. It only works in a Client Component but none of its parents are marked with "use client"

In the Next.js App Router, a component using hooks or browser APIs is rendered as a Server Component.

key is not a propReact

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.

NextRouter was not mountedReact

Error: NextRouter was not mounted.

next/router’s useRouter was used inside the App Router (app/ directory), which uses next/navigation instead.

No HTTP methods exported in route.tsNext.js

Next.js: Error: No HTTP methods exported in '/app/api/users/route.ts'. Export a named export for each HTTP method (GET, POST...)

A Route Handler file exports no recognised HTTP method function.

You are attempting to export "metadata" from a component marked with "use client"Next.js

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