All Errors

Express requires error-handling middleware to have exactly four parameters: (err, req, res, next). Without all four parameters, Express treats the function as regular middleware instead of an error handler. This error occurs when your error handler doesn't follow the correct signature.

This warning indicates your code uses a deprecated PostgreSQL feature. Update to the recommended modern alternative to ensure compatibility with future versions.

This SSH error occurs when a user is explicitly blocked by the DenyUsers directive in sshd_config. Remove the user from the DenyUsers list and restart the SSH service to restore access.

This error occurs when your Express or Node.js application attempts to modify HTTP response headers after the response body has already been sent to the client. This typically happens when multiple responses are sent per request or when headers are set after res.send(), res.json(), or similar methods.

This error occurs when your application makes too many requests to Supabase Auth or Management API within a short timeframe, triggering built-in rate limiting that returns a 429 status code.

The Node.js domain module is deprecated and should not be used in new code. This warning appears when you import or use the domain module. Use async_hooks or AsyncResource instead for proper async context tracking.

This error occurs when Express.static() middleware is configured to serve files from a directory that doesn't exist. The application fails to start because the specified path cannot be found on the filesystem.

React throws this error when a `<Suspense>` boundary never catches a Promise or an async child, so the runtime refuses to render the boundary or its fallback.

This Fastify error occurs when you attempt to send a response twice on the same request. Once reply.send() has been called, the response is finalized and cannot be sent again. Ensure each route handler sends a response only once.

React throws this parser error when it tries to JSON.parse() a response that is actually HTML, which usually happens because the front-end asset server (webpack dev server or CRA proxy) answers the request instead of your API.

This error occurs in Fastify when you try to register a decorator (plugin, hook, or utility method) with a name that already exists. Fastify prevents duplicate decorator registration to avoid silent overwrites. The fix involves checking for existing decorators, using unique names, or explicitly overwriting when intentional.

The FST_ERR_HOOK_TIMEOUT error occurs when a Fastify hook (onRequest, onSend, etc.) takes longer than the allowed timeout to complete. This error indicates that your hook is either performing long-running operations or is stuck in an infinite loop. Resolving this requires optimizing the hook code or adjusting timeout configuration.

The react-hooks/exhaustive-deps rule warns when values used inside useMemo aren't listed in the dependency array, which causes the memoized result to become stale as props or state change.

This error occurs when a client makes a request to an Express server for a URL path that does not match any defined routes. Express returns a 404 Not Found HTTP status code, indicating the requested resource could not be found on the server.

This error occurs when fs.copyFile() is called with the COPYFILE_EXCL flag and the destination file already exists. The COPYFILE_EXCL flag is a safety mechanism that prevents overwriting existing files, causing the operation to fail if the destination path is occupied.

This error occurs when fs.mkdir() or fs.mkdirSync() attempts to create a directory at a path where a file already exists. Node.js cannot create a directory with the same name as an existing file, causing the operation to fail with EEXIST.

React complains when an input starts with no value (uncontrolled) and later receives a value prop. Keeping inputs consistently controlled or using defaultValue avoids the warning and keeps form state predictable.

This error occurs when Node.js attempts to create a symbolic link on Windows without administrator privileges. Windows restricts symlink creation to admin accounts or users with specific developer mode permissions. The error commonly appears when using fs.symlink() or tools that auto-link dependencies, especially in development environments or CI/CD pipelines.

This warning occurs during React hydration when server-rendered HTML contains attributes that the client-side code doesn't expect. In older React versions (pre-16), data-reactroot and data-reactid were internal attributes used by React. Modern React has removed these attributes, but the warning can still appear due to browser extensions or version mismatches.

This error occurs when an HTTP/2 frame payload exceeds the maximum allowed frame size limit. HTTP/2 enforces strict frame size constraints (default 16KB), and this error indicates the server or client sent a frame that violates these limits, preventing the connection from continuing.