Errors

Applications running in Node.js will generally experience four categories of errors:

• Standard JavaScript errors such as <EvalError>, <SyntaxError>, <RangeError>, <ReferenceError>, <TypeError>, and <URIError>.
• System errors triggered by underlying operating system constraints such as attempting to open a file that does not exist or attempting to send data over a closed socket.
• User-specified errors triggered by application code.
• AssertionErrors are a special class of error that can be triggered when Node.js detects an exceptional logic violation that should never occur. These are raised typically by the assert module.

All JavaScript and System errors raised by Node.js inherit from, or are instances of, the standard JavaScript <Error> class and are guaranteed to provide at least the properties available on that class.

Error Propagation and Interception

Node.js supports several mechanisms for propagating and handling errors that occur while an application is running. How these errors are reported and handled depends entirely on the type of Error and the style of the API that is called.

All JavaScript errors are handled as exceptions that immediately generate and throw an error using the standard JavaScript throw mechanism. These are handled using the try…catch construct provided by the JavaScript language.

// Throws with a ReferenceError because z is not defined.
try {
  const m = 1;
  const n = m + z;
} catch (err) {
  // Handle the error here.
}

Any use of the JavaScript throw mechanism will raise an exception that must be handled using try…catch or the Node.js process will exit immediately.

With few exceptions, Synchronous APIs (any blocking method that does not accept a callback function, such as fs.readFileSync), will use throw to report errors.

Errors that occur within Asynchronous APIs may be reported in multiple ways:

• Most asynchronous methods that accept a callback function will accept an Error object passed as the first argument to that function. If that first argument is not null and is an instance of Error, then an error occurred that should be handled.

const fs = require('fs');
fs.readFile('a file that does not exist', (err, data) => {
  if (err) {
    console.error('There was an error reading the file!', err);
    return;
  }
  // Otherwise handle the data
});

• When an asynchronous method is called on an object that is an EventEmitter, errors can be routed to that object's 'error' event.

  const net = require('net');
  const connection = net.connect('localhost');
  
  // Adding an 'error' event handler to a stream:
  connection.on('error', (err) => {
    // If the connection is reset by the server, or if it can't
    // connect at all, or on any sort of error encountered by
    // the connection, the error will be sent here.
    console.error(err);
  });
  
  connection.pipe(process.stdout);
  

• A handful of typically asynchronous methods in the Node.js API may still use the throw mechanism to raise exceptions that must be handled using try…catch. There is no comprehensive list of such methods; please refer to the documentation of each method to determine the appropriate error handling mechanism required.

The use of the 'error' event mechanism is most common for stream-based and event emitter-based APIs, which themselves represent a series of asynchronous operations over time (as opposed to a single operation that may pass or fail).

For all EventEmitter objects, if an 'error' event handler is not provided, the error will be thrown, causing the Node.js process to report an uncaught exception and crash unless either: The domain module is used appropriately or a handler has been registered for the 'uncaughtException' event.

const EventEmitter = require('events');
const ee = new EventEmitter();

setImmediate(() => {
  // This will crash the process because no 'error' event
  // handler has been added.
  ee.emit('error', new Error('This will crash'));
});

Errors generated in this way cannot be intercepted using try…catch as they are thrown after the calling code has already exited.

Developers must refer to the documentation for each method to determine exactly how errors raised by those methods are propagated.

Error-first callbacks

Most asynchronous methods exposed by the Node.js core API follow an idiomatic pattern referred to as an error-first callback. With this pattern, a callback function is passed to the method as an argument. When the operation either completes or an error is raised, the callback function is called with the Error object (if any) passed as the first argument. If no error was raised, the first argument will be passed as null.

const fs = require('fs');

function errorFirstCallback(err, data) {
  if (err) {
    console.error('There was an error', err);
    return;
  }
  console.log(data);
}

fs.readFile('/some/file/that/does-not-exist', errorFirstCallback);
fs.readFile('/some/file/that/does-exist', errorFirstCallback);

The JavaScript try…catch mechanism cannot be used to intercept errors generated by asynchronous APIs. A common mistake for beginners is to try to use throw inside an error-first callback:

// THIS WILL NOT WORK:
const fs = require('fs');

try {
  fs.readFile('/some/file/that/does-not-exist', (err, data) => {
    // mistaken assumption: throwing here...
    if (err) {
      throw err;
    }
  });
} catch (err) {
  // This will not catch the throw!
  console.error(err);
}

This will not work because the callback function passed to fs.readFile() is called asynchronously. By the time the callback has been called, the surrounding code (including the try { } catch (err) { } block will have already exited. Throwing an error inside the callback can crash the Node.js process in most cases. If domains are enabled, or a handler has been registered with process.on('uncaughtException'), such errors can be intercepted.

Class: Error

A generic JavaScript Error object that does not denote any specific circumstance of why the error occurred. Error objects capture a "stack trace" detailing the point in the code at which the Error was instantiated, and may provide a text description of the error.

For crypto only, Error objects will include the OpenSSL error stack in a separate property called opensslErrorStack if it is available when the error is thrown.

All errors generated by Node.js, including all System and JavaScript errors, will either be instances of, or inherit from, the Error class.

new Error(message)

• message <string>

Creates a new Error object and sets the error.message property to the provided text message. If an object is passed as message, the text message is generated by calling message.toString(). The error.stack property will represent the point in the code at which new Error() was called. Stack traces are dependent on V8's stack trace API. Stack traces extend only to either (a) the beginning of synchronous code execution, or (b) the number of frames given by the property Error.stackTraceLimit, whichever is smaller.

Error.captureStackTrace(targetObject[, constructorOpt])

• targetObject <Object>
• constructorOpt <Function>

Creates a .stack property on targetObject, which when accessed returns a string representing the location in the code at which Error.captureStackTrace() was called.

const myObject = {};
Error.captureStackTrace(myObject);
myObject.stack;  // similar to `new Error().stack`

The first line of the trace will be prefixed with ${myObject.name}: ${myObject.message}.

The optional constructorOpt argument accepts a function. If given, all frames above constructorOpt, including constructorOpt, will be omitted from the generated stack trace.

The constructorOpt argument is useful for hiding implementation details of error generation from an end user. For instance:

function MyError() {
  Error.captureStackTrace(this, MyError);
}

// Without passing MyError to captureStackTrace, the MyError
// frame would show up in the .stack property. By passing
// the constructor, we omit that frame, and retain all frames below it.
new MyError().stack;

Error.stackTraceLimit

• <number>

The Error.stackTraceLimit property specifies the number of stack frames collected by a stack trace (whether generated by new Error().stack or Error.captureStackTrace(obj)).

The default value is 10 but may be set to any valid JavaScript number. Changes will affect any stack trace captured after the value has been changed.

If set to a non-number value, or set to a negative number, stack traces will not capture any frames.

error.code

• <string>

The error.code property is a string label that identifies the kind of error. error.code is the most stable way to identify an error. It will only change between major versions of Node.js. In contrast, error.message strings may change between any versions of Node.js. See Node.js Error Codes for details about specific codes.

error.message

• <string>

The error.message property is the string description of the error as set by calling new Error(message). The message passed to the constructor will also appear in the first line of the stack trace of the Error, however changing this property after the Error object is created may not change the first line of the stack trace (for example, when error.stack is read before this property is changed).

const err = new Error('The message');
console.error(err.message);
// Prints: The message

error.stack

• <string>

The error.stack property is a string describing the point in the code at which the Error was instantiated.

Error: Things keep happening!
   at /home/gbusey/file.js:525:2
   at Frobnicator.refrobulate (/home/gbusey/business-logic.js:424:21)
   at Actor.<anonymous> (/home/gbusey/actors.js:400:8)
   at increaseSynergy (/home/gbusey/actors.js:701:6)

The first line is formatted as <error class name>: <error message>, and is followed by a series of stack frames (each line beginning with "at "). Each frame describes a call site within the code that lead to the error being generated. V8 attempts to display a name for each function (by variable name, function name, or object method name), but occasionally it will not be able to find a suitable name. If V8 cannot determine a name for the function, only location information will be displayed for that frame. Otherwise, the determined function name will be displayed with location information appended in parentheses.

Frames are only generated for JavaScript functions. If, for example, execution synchronously passes through a C++ addon function called cheetahify which itself calls a JavaScript function, the frame representing the cheetahify call will not be present in the stack traces:

const cheetahify = require('./native-binding.node');

function makeFaster() {
  // cheetahify *synchronously* calls speedy.
  cheetahify(function speedy() {
    throw new Error('oh no!');
  });
}

makeFaster();
// will throw:
//   /home/gbusey/file.js:6
//       throw new Error('oh no!');
//           ^
//   Error: oh no!
//       at speedy (/home/gbusey/file.js:6:11)
//       at makeFaster (/home/gbusey/file.js:5:3)
//       at Object.<anonymous> (/home/gbusey/file.js:10:1)
//       at Module._compile (module.js:456:26)
//       at Object.Module._extensions..js (module.js:474:10)
//       at Module.load (module.js:356:32)
//       at Function.Module._load (module.js:312:12)
//       at Function.Module.runMain (module.js:497:10)
//       at startup (node.js:119:16)
//       at node.js:906:3

The location information will be one of:

• native, if the frame represents a call internal to V8 (as in [].forEach).
• plain-filename.js:line:column, if the frame represents a call internal to Node.js.
• /absolute/path/to/file.js:line:column, if the frame represents a call in a user program, or its dependencies.

The string representing the stack trace is lazily generated when the error.stack property is accessed.

The number of frames captured by the stack trace is bounded by the smaller of Error.stackTraceLimit or the number of available frames on the current event loop tick.

System-level errors are generated as augmented Error instances, which are detailed here.

Class: AssertionError

A subclass of Error that indicates the failure of an assertion. For details, see Class: assert.AssertionError.

Class: RangeError

A subclass of Error that indicates that a provided argument was not within the set or range of acceptable values for a function; whether that is a numeric range, or outside the set of options for a given function parameter.

require('net').connect(-1);
// throws "RangeError: "port" option should be >= 0 and < 65536: -1"

Node.js will generate and throw RangeError instances immediately as a form of argument validation.

Class: ReferenceError

A subclass of Error that indicates that an attempt is being made to access a variable that is not defined. Such errors commonly indicate typos in code, or an otherwise broken program.

While client code may generate and propagate these errors, in practice, only V8 will do so.

doesNotExist;
// throws ReferenceError, doesNotExist is not a variable in this program.

Unless an application is dynamically generating and running code, ReferenceError instances should always be considered a bug in the code or its dependencies.

Class: SyntaxError

A subclass of Error that indicates that a program is not valid JavaScript. These errors may only be generated and propagated as a result of code evaluation. Code evaluation may happen as a result of eval, Function, require, or vm. These errors are almost always indicative of a broken program.

try {
  require('vm').runInThisContext('binary ! isNotOk');
} catch (err) {
  // err will be a SyntaxError
}

SyntaxError instances are unrecoverable in the context that created them – they may only be caught by other contexts.

Class: TypeError

A subclass of Error that indicates that a provided argument is not an allowable type. For example, passing a function to a parameter which expects a string would be considered a TypeError.

require('url').parse(() => { });
// throws TypeError, since it expected a string

Node.js will generate and throw TypeError instances immediately as a form of argument validation.

Exceptions vs. Errors

A JavaScript exception is a value that is thrown as a result of an invalid operation or as the target of a throw statement. While it is not required that these values are instances of Error or classes which inherit from Error, all exceptions thrown by Node.js or the JavaScript runtime will be instances of Error.

Some exceptions are unrecoverable at the JavaScript layer. Such exceptions will always cause the Node.js process to crash. Examples include assert() checks or abort() calls in the C++ layer.

System Errors

Node.js generates system errors when exceptions occur within its runtime environment. These usually occur when an application violates an operating system constraint. For example, a system error will occur if an application attempts to read a file that does not exist.

System errors are usually generated at the syscall level. For a comprehensive list, see the errno(3) man page.

In Node.js, system errors are Error objects with extra properties.

Class: SystemError

• address <string> If present, the address to which a network connection failed
• code <string> The string error code
• dest <string> If present, the file path destination when reporting a file system error
• errno <number> | <string> The system-provided error number
• info <Object> If present, extra details about the error condition
• message <string> A system-provided human-readable description of the error
• path <string> If present, the file path when reporting a file system error
• port <number> If present, the network connection port that is not available
• syscall <string> The name of the system call that triggered the error

error.address

• <string>

If present, error.address is a string describing the address to which a network connection failed.

error.code

• <string>

The error.code property is a string representing the error code.

error.dest

• <string>

If present, error.dest is the file path destination when reporting a file system error.

error.errno

• <string> | <number>

The error.errno property is a number or a string. If it is a number, it is a negative value which corresponds to the error code defined in libuv Error handling. See the libuv errno.h header file (deps/uv/include/uv/errno.h in the Node.js source tree) for details. In case of a string, it is the same as error.code.

error.info

• <Object>

If present, error.info is an object with details about the error condition.

error.message

• <string>

error.message is a system-provided human-readable description of the error.

error.path

• <string>

If present, error.path is a string containing a relevant invalid pathname.

error.port

• <number>

If present, error.port is the network connection port that is not available.

error.syscall

• <string>

The error.syscall property is a string describing the syscall that failed.

Common System Errors

This is a list of system errors commonly-encountered when writing a Node.js program. For a comprehensive list, see the errno(3) man page.

• EACCES (Permission denied): An attempt was made to access a file in a way forbidden by its file access permissions.

• EADDRINUSE (Address already in use): An attempt to bind a server (net, http, or https) to a local address failed due to another server on the local system already occupying that address.

• ECONNREFUSED (Connection refused): No connection could be made because the target machine actively refused it. This usually results from trying to connect to a service that is inactive on the foreign host.

• ECONNRESET (Connection reset by peer): A connection was forcibly closed by a peer. This normally results from a loss of the connection on the remote socket due to a timeout or reboot. Commonly encountered via the http and net modules.

• EEXIST (File exists): An existing file was the target of an operation that required that the target not exist.

• EISDIR (Is a directory): An operation expected a file, but the given pathname was a directory.

• EMFILE (Too many open files in system): Maximum number of file descriptors allowable on the system has been reached, and requests for another descriptor cannot be fulfilled until at least one has been closed. This is encountered when opening many files at once in parallel, especially on systems (in particular, macOS) where there is a low file descriptor limit for processes. To remedy a low limit, run ulimit -n 2048 in the same shell that will run the Node.js process.

• ENOENT (No such file or directory): Commonly raised by fs operations to indicate that a component of the specified pathname does not exist. No entity (file or directory) could be found by the given path.

• ENOTDIR (Not a directory): A component of the given pathname existed, but was not a directory as expected. Commonly raised by fs.readdir.

• ENOTEMPTY (Directory not empty): A directory with entries was the target of an operation that requires an empty directory, usually fs.unlink.

• EPERM (Operation not permitted): An attempt was made to perform an operation that requires elevated privileges.

• EPIPE (Broken pipe): A write on a pipe, socket, or FIFO for which there is no process to read the data. Commonly encountered at the net and http layers, indicative that the remote side of the stream being written to has been closed.

• ETIMEDOUT (Operation timed out): A connect or send request failed because the connected party did not properly respond after a period of time. Usually encountered by http or net. Often a sign that a socket.end() was not properly called.

Node.js Error Codes

ERR_AMBIGUOUS_ARGUMENT

A function argument is being used in a way that suggests that the function signature may be misunderstood. This is thrown by the assert module when the message parameter in assert.throws(block, message) matches the error message thrown by block because that usage suggests that the user believes message is the expected message rather than the message the AssertionError will display if block does not throw.

ERR_ARG_NOT_ITERABLE

An iterable argument (i.e. a value that works with for...of loops) was required, but not provided to a Node.js API.

ERR_ASSERTION

A special type of error that can be triggered whenever Node.js detects an exceptional logic violation that should never occur. These are raised typically by the assert module.

ERR_ASYNC_CALLBACK

An attempt was made to register something that is not a function as an AsyncHooks callback.

ERR_ASYNC_TYPE

The type of an asynchronous resource was invalid. Note that users are also able to define their own types if using the public embedder API.

ERR_BROTLI_COMPRESSION_FAILED

Data passed to a Brotli stream was not successfully compressed.

ERR_BROTLI_INVALID_PARAM

An invalid parameter key was passed during construction of a Brotli stream.

ERR_BUFFER_OUT_OF_BOUNDS

An operation outside the bounds of a Buffer was attempted.

ERR_BUFFER_TOO_LARGE

An attempt has been made to create a Buffer larger than the maximum allowed size.

ERR_CANNOT_TRANSFER_OBJECT

The value passed to postMessage() contained an object that is not supported for transferring.

ERR_CANNOT_WATCH_SIGINT

Node.js was unable to watch for the SIGINT signal.

ERR_CHILD_CLOSED_BEFORE_REPLY

A child process was closed before the parent received a reply.

ERR_CHILD_PROCESS_IPC_REQUIRED

Used when a child process is being forked without specifying an IPC channel.

ERR_CHILD_PROCESS_STDIO_MAXBUFFER

Used when the main process is trying to read data from the child process's STDERR/STDOUT, and the data's length is longer than the maxBuffer option.

ERR_CLOSED_MESSAGE_PORT

There was an attempt to use a MessagePort instance in a closed state, usually after .close() has been called.

ERR_CONSOLE_WRITABLE_STREAM

Console was instantiated without stdout stream, or Console has a non-writable stdout or stderr stream.

ERR_CONSTRUCT_CALL_REQUIRED

A constructor for a class was called without new.

ERR_CPU_USAGE

The native call from process.cpuUsage could not be processed.

ERR_CRYPTO_CUSTOM_ENGINE_NOT_SUPPORTED

A client certificate engine was requested that is not supported by the version of OpenSSL being used.

ERR_CRYPTO_ECDH_INVALID_FORMAT

An invalid value for the format argument was passed to the crypto.ECDH() class getPublicKey() method.

ERR_CRYPTO_ECDH_INVALID_PUBLIC_KEY

An invalid value for the key argument has been passed to the crypto.ECDH() class computeSecret() method. It means that the public key lies outside of the elliptic curve.

ERR_CRYPTO_ENGINE_UNKNOWN

An invalid crypto engine identifier was passed to require('crypto').setEngine().

ERR_CRYPTO_FIPS_FORCED

The --force-fips command-line argument was used but there was an attempt to enable or disable FIPS mode in the crypto module.

ERR_CRYPTO_FIPS_UNAVAILABLE

An attempt was made to enable or disable FIPS mode, but FIPS mode was not available.

ERR_CRYPTO_HASH_DIGEST_NO_UTF16

The UTF-16 encoding was used with hash.digest(). While the hash.digest() method does allow an encoding argument to be passed in, causing the method to return a string rather than a Buffer, the UTF-16 encoding (e.g. ucs or utf16le) is not supported.

ERR_CRYPTO_HASH_FINALIZED

hash.digest() was called multiple times. The hash.digest() method must be called no more than one time per instance of a Hash object.

ERR_CRYPTO_HASH_UPDATE_FAILED

hash.update() failed for any reason. This should rarely, if ever, happen.

ERR_CRYPTO_INCOMPATIBLE_KEY_OPTIONS

The selected public or private key encoding is incompatible with other options.

ERR_CRYPTO_INVALID_DIGEST

An invalid crypto digest algorithm was specified.

ERR_CRYPTO_INVALID_STATE

A crypto method was used on an object that was in an invalid state. For instance, calling cipher.getAuthTag() before calling cipher.final().

ERR_CRYPTO_PBKDF2_ERROR

The PBKDF2 algorithm failed for unspecified reasons. OpenSSL does not provide more details and therefore neither does Node.js.

ERR_CRYPTO_SCRYPT_INVALID_PARAMETER

One or more crypto.scrypt() or crypto.scryptSync() parameters are outside their legal range.

ERR_CRYPTO_SCRYPT_NOT_SUPPORTED

Node.js was compiled without scrypt support. Not possible with the official release binaries but can happen with custom builds, including distro builds.

ERR_CRYPTO_SIGN_KEY_REQUIRED

A signing key was not provided to the sign.sign() method.

ERR_CRYPTO_TIMING_SAFE_EQUAL_LENGTH

crypto.timingSafeEqual() was called with Buffer, TypedArray, or DataView arguments of different lengths.

ERR_DNS_SET_SERVERS_FAILED

c-ares failed to set the DNS server.

ERR_DOMAIN_CALLBACK_NOT_AVAILABLE

The domain module was not usable since it could not establish the required error handling hooks, because process.setUncaughtExceptionCaptureCallback() had been called at an earlier point in time.

ERR_DOMAIN_CANNOT_SET_UNCAUGHT_EXCEPTION_CAPTURE

process.setUncaughtExceptionCaptureCallback() could not be called because the domain module has been loaded at an earlier point in time.

The stack trace is extended to include the point in time at which the domain module had been loaded.

ERR_ENCODING_INVALID_ENCODED_DATA

Data provided to util.TextDecoder() API was invalid according to the encoding provided.

ERR_ENCODING_NOT_SUPPORTED

Encoding provided to util.TextDecoder() API was not one of the WHATWG Supported Encodings.

ERR_FALSY_VALUE_REJECTION

A Promise that was callbackified via util.callbackify() was rejected with a falsy value.

ERR_FS_FILE_TOO_LARGE

An attempt has been made to read a file whose size is larger than the maximum allowed size for a Buffer.

ERR_FS_INVALID_SYMLINK_TYPE

An invalid symlink type was passed to the fs.symlink() or fs.symlinkSync() methods.

ERR_HTTP_HEADERS_SENT

An attempt was made to add more headers after the headers had already been sent.

ERR_HTTP_INVALID_HEADER_VALUE

An invalid HTTP header value was specified.

ERR_HTTP_INVALID_STATUS_CODE

Status code was outside the regular status code range (100-999).

ERR_HTTP_TRAILER_INVALID

The Trailer header was set even though the transfer encoding does not support that.

ERR_HTTP2_ALTSVC_INVALID_ORIGIN

HTTP/2 ALTSVC frames require a valid origin.

ERR_HTTP2_ALTSVC_LENGTH

HTTP/2 ALTSVC frames are limited to a maximum of 16,382 payload bytes.

ERR_HTTP2_CONNECT_AUTHORITY

For HTTP/2 requests using the CONNECT method, the :authority pseudo-header is required.

ERR_HTTP2_CONNECT_PATH

For HTTP/2 requests using the CONNECT method, the :path pseudo-header is forbidden.

ERR_HTTP2_CONNECT_SCHEME

For HTTP/2 requests using the CONNECT method, the :scheme pseudo-header is forbidden.

ERR_HTTP2_ERROR

A non-specific HTTP/2 error has occurred.

ERR_HTTP2_GOAWAY_SESSION

New HTTP/2 Streams may not be opened after the Http2Session has received a GOAWAY frame from the connected peer.

ERR_HTTP2_HEADERS_AFTER_RESPOND

An additional headers was specified after an HTTP/2 response was initiated.

ERR_HTTP2_HEADERS_SENT

An attempt was made to send multiple response headers.

ERR_HTTP2_HEADER_SINGLE_VALUE

Multiple values were provided for an HTTP/2 header field that was required to have only a single value.

ERR_HTTP2_INFO_STATUS_NOT_ALLOWED

Informational HTTP status codes (1xx) may not be set as the response status code on HTTP/2 responses.

ERR_HTTP2_INVALID_CONNECTION_HEADERS

HTTP/1 connection specific headers are forbidden to be used in HTTP/2 requests and responses.

ERR_HTTP2_INVALID_HEADER_VALUE

An invalid HTTP/2 header value was specified.

ERR_HTTP2_INVALID_INFO_STATUS

An invalid HTTP informational status code has been specified. Informational status codes must be an integer between 100 and 199 (inclusive).

ERR_HTTP2_INVALID_ORIGIN

HTTP/2 ORIGIN frames require a valid origin.

ERR_HTTP2_INVALID_PACKED_SETTINGS_LENGTH

Input Buffer and Uint8Array instances passed to the http2.getUnpackedSettings() API must have a length that is a multiple of six.

ERR_HTTP2_INVALID_PSEUDOHEADER

Only valid HTTP/2 pseudoheaders (:status, :path, :authority, :scheme, and :method) may be used.

ERR_HTTP2_INVALID_SESSION

An action was performed on an Http2Session object that had already been destroyed.

ERR_HTTP2_INVALID_SETTING_VALUE

An invalid value has been specified for an HTTP/2 setting.

ERR_HTTP2_INVALID_STREAM

An operation was performed on a stream that had already been destroyed.

ERR_HTTP2_MAX_PENDING_SETTINGS_ACK

Whenever an HTTP/2 SETTINGS frame is sent to a connected peer, the peer is required to send an acknowledgment that it has received and applied the new SETTINGS. By default, a maximum number of unacknowledged SETTINGS frames may be sent at any given time. This error code is used when that limit has been reached.

ERR_HTTP2_NESTED_PUSH

An attempt was made to initiate a new push stream from within a push stream. Nested push streams are not permitted.

ERR_HTTP2_NO_SOCKET_MANIPULATION

An attempt was made to directly manipulate (read, write, pause, resume, etc.) a socket attached to an Http2Session.

ERR_HTTP2_ORIGIN_LENGTH

HTTP/2 ORIGIN frames are limited to a length of 16382 bytes.

ERR_HTTP2_OUT_OF_STREAMS

The number of streams created on a single HTTP/2 session reached the maximum limit.

ERR_HTTP2_PAYLOAD_FORBIDDEN

A message payload was specified for an HTTP response code for which a payload is forbidden.

ERR_HTTP2_PING_CANCEL

An HTTP/2 ping was canceled.

ERR_HTTP2_PING_LENGTH

HTTP/2 ping payloads must be exactly 8 bytes in length.

ERR_HTTP2_PSEUDOHEADER_NOT_ALLOWED

An HTTP/2 pseudo-header has been used inappropriately. Pseudo-headers are header key names that begin with the : prefix.

ERR_HTTP2_PUSH_DISABLED

An attempt was made to create a push stream, which had been disabled by the client.

ERR_HTTP2_SEND_FILE

An attempt was made to use the Http2Stream.prototype.responseWithFile() API to send a directory.

ERR_HTTP2_SEND_FILE_NOSEEK

An attempt was made to use the Http2Stream.prototype.responseWithFile() API to send something other than a regular file, but offset or length options were provided.

ERR_HTTP2_SESSION_ERROR

The Http2Session closed with a non-zero error code.

ERR_HTTP2_SETTINGS_CANCEL

The Http2Session settings canceled.

ERR_HTTP2_SOCKET_BOUND

An attempt was made to connect a Http2Session object to a net.Socket or tls.TLSSocket that had already been bound to another Http2Session object.

ERR_HTTP2_SOCKET_UNBOUND

An attempt was made to use the socket property of an Http2Session that has already been closed.

ERR_HTTP2_STATUS_101

Use of the 101 Informational status code is forbidden in HTTP/2.

ERR_HTTP2_STATUS_INVALID

An invalid HTTP status code has been specified. Status codes must be an integer between 100 and 599 (inclusive).

ERR_HTTP2_STREAM_CANCEL

An Http2Stream was destroyed before any data was transmitted to the connected peer.

ERR_HTTP2_STREAM_ERROR

A non-zero error code was been specified in an RST_STREAM frame.

ERR_HTTP2_STREAM_SELF_DEPENDENCY

When setting the priority for an HTTP/2 stream, the stream may be marked as a dependency for a parent stream. This error code is used when an attempt is made to mark a stream and dependent of itself.

ERR_HTTP2_TRAILERS_ALREADY_SENT

Trailing headers have already been sent on the Http2Stream.

ERR_HTTP2_TRAILERS_NOT_READY

The http2stream.sendTrailers() method cannot be called until after the 'wantTrailers' event is emitted on an Http2Stream object. The 'wantTrailers' event will only be emitted if the waitForTrailers option is set for the Http2Stream.

ERR_HTTP2_UNSUPPORTED_PROTOCOL

http2.connect() was passed a URL that uses any protocol other than http: or https:.

ERR_INDEX_OUT_OF_RANGE

A given index was out of the accepted range (e.g. negative offsets).

ERR_INSPECTOR_ALREADY_CONNECTED

While using the inspector module, an attempt was made to connect when the inspector was already connected.

ERR_INSPECTOR_CLOSED

While using the inspector module, an attempt was made to use the inspector after the session had already closed.

ERR_INSPECTOR_NOT_AVAILABLE

The inspector module is not available for use.

ERR_INSPECTOR_NOT_CONNECTED

While using the inspector module, an attempt was made to use the inspector before it was connected.

ERR_INVALID_ADDRESS_FAMILY

The provided address family is not understood by the Node.js API.

ERR_INVALID_ARG_TYPE

An argument of the wrong type was passed to a Node.js API.

ERR_INVALID_ARG_VALUE

An invalid or unsupported value was passed for a given argument.

ERR_INVALID_ARRAY_LENGTH

An array was not of the expected length or in a valid range.

ERR_INVALID_ASYNC_ID

An invalid asyncId or triggerAsyncId was passed using AsyncHooks. An id less than -1 should never happen.

ERR_INVALID_BUFFER_SIZE

A swap was performed on a Buffer but its size was not compatible with the operation.

ERR_INVALID_CALLBACK

A callback function was required but was not been provided to a Node.js API.

ERR_INVALID_CHAR

Invalid characters were detected in headers.

ERR_INVALID_CURSOR_POS

A cursor on a given stream cannot be moved to a specified row without a specified column.

ERR_INVALID_DOMAIN_NAME

hostname can not be parsed from a provided URL.

ERR_INVALID_FD

A file descriptor ('fd') was not valid (e.g. it was a negative value).

ERR_INVALID_FD_TYPE

A file descriptor ('fd') type was not valid.

ERR_INVALID_FILE_URL_HOST

A Node.js API that consumes file: URLs (such as certain functions in the fs module) encountered a file URL with an incompatible host. This situation can only occur on Unix-like systems where only localhost or an empty host is supported.

ERR_INVALID_FILE_URL_PATH

A Node.js API that consumes file: URLs (such as certain functions in the fs module) encountered a file URL with an incompatible path. The exact semantics for determining whether a path can be used is platform-dependent.

ERR_INVALID_HANDLE_TYPE

An attempt was made to send an unsupported "handle" over an IPC communication channel to a child process. See subprocess.send() and process.send() for more information.

ERR_INVALID_HTTP_TOKEN

An invalid HTTP token was supplied.

ERR_INVALID_IP_ADDRESS

An IP address is not valid.

ERR_INVALID_OPT_VALUE

An invalid or unexpected value was passed in an options object.

ERR_INVALID_OPT_VALUE_ENCODING

An invalid or unknown file encoding was passed.

ERR_INVALID_PERFORMANCE_MARK

While using the Performance Timing API (perf_hooks), a performance mark is invalid.

ERR_INVALID_PROTOCOL

An invalid options.protocol was passed.

ERR_INVALID_REPL_EVAL_CONFIG

Both breakEvalOnSigint and eval options were set in the REPL config, which is not supported.

ERR_INVALID_RETURN_PROPERTY

Thrown in case a function option does not provide a valid value for one of its returned object properties on execution.

ERR_INVALID_RETURN_PROPERTY_VALUE

Thrown in case a function option does not provide an expected value type for one of its returned object properties on execution.

ERR_INVALID_RETURN_VALUE

Thrown in case a function option does not return an expected value type on execution, such as when a function is expected to return a promise.

ERR_INVALID_SYNC_FORK_INPUT

A Buffer, TypedArray, DataView or string was provided as stdio input to an asynchronous fork. See the documentation for the child_process module for more information.

ERR_INVALID_THIS

A Node.js API function was called with an incompatible this value.

const urlSearchParams = new URLSearchParams('foo=bar&baz=new');

const buf = Buffer.alloc(1);
urlSearchParams.has.call(buf, 'foo');
// Throws a TypeError with code 'ERR_INVALID_THIS'

ERR_INVALID_TRANSFER_OBJECT

An invalid transfer object was passed to postMessage().

ERR_INVALID_TUPLE

An element in the iterable provided to the WHATWG URLSearchParams constructor did not represent a [name, value] tuple – that is, if an element is not iterable, or does not consist of exactly two elements.

ERR_INVALID_URI

An invalid URI was passed.

ERR_INVALID_URL

An invalid URL was passed to the WHATWG URL constructor to be parsed. The thrown error object typically has an additional property 'input' that contains the URL that failed to parse.

ERR_INVALID_URL_SCHEME

An attempt was made to use a URL of an incompatible scheme (protocol) for a specific purpose. It is only used in the WHATWG URL API support in the fs module (which only accepts URLs with 'file' scheme), but may be used in other Node.js APIs as well in the future.

ERR_IPC_CHANNEL_CLOSED

An attempt was made to use an IPC communication channel that was already closed.

ERR_IPC_DISCONNECTED

An attempt was made to disconnect an IPC communication channel that was already disconnected. See the documentation for the child_process module for more information.

ERR_IPC_ONE_PIPE

An attempt was made to create a child Node.js process using more than one IPC communication channel. See the documentation for the child_process module for more information.

ERR_IPC_SYNC_FORK

An attempt was made to open an IPC communication channel with a synchronously forked Node.js process. See the documentation for the child_process module for more information.

ERR_MEMORY_ALLOCATION_FAILED

An attempt was made to allocate memory (usually in the C++ layer) but it failed.

ERR_METHOD_NOT_IMPLEMENTED

A method is required but not implemented.

ERR_MISSING_ARGS

A required argument of a Node.js API was not passed. This is only used for strict compliance with the API specification (which in some cases may accept func(undefined) but not func()). In most native Node.js APIs, func(undefined) and func() are treated identically, and the ERR_INVALID_ARG_TYPE error code may be used instead.

ERR_MISSING_DYNAMIC_INSTANTIATE_HOOK

An ES6 module loader hook specified format: 'dynamic' but did not provide a dynamicInstantiate hook.

ERR_MISSING_MESSAGE_PORT_IN_TRANSFER_LIST

A MessagePort was found in the object passed to a postMessage() call, but not provided in the transferList for that call.

ERR_MISSING_MODULE

An ES6 module could not be resolved.

ERR_MISSING_PLATFORM_FOR_WORKER

The V8 platform used by this instance of Node.js does not support creating Workers. This is caused by lack of embedder support for Workers. In particular, this error will not occur with standard builds of Node.js.

ERR_MODULE_RESOLUTION_LEGACY

A failure occurred resolving imports in an ES6 module.

ERR_MULTIPLE_CALLBACK

A callback was called more than once.

A callback is almost always meant to only be called once as the query can either be fulfilled or rejected but not both at the same time. The latter would be possible by calling a callback more than once.

ERR_NAPI_CONS_FUNCTION

While using N-API, a constructor passed was not a function.

ERR_NAPI_INVALID_DATAVIEW_ARGS

While calling napi_create_dataview(), a given offset was outside the bounds of the dataview or offset + length was larger than a length of given buffer.

ERR_NAPI_INVALID_TYPEDARRAY_ALIGNMENT

While calling napi_create_typedarray(), the provided offset was not a multiple of the element size.

ERR_NAPI_INVALID_TYPEDARRAY_LENGTH

While calling napi_create_typedarray(), (length * size_of_element) + byte_offset was larger than the length of given buffer.

ERR_NAPI_TSFN_CALL_JS

An error occurred while invoking the JavaScript portion of the thread-safe function.

ERR_NAPI_TSFN_GET_UNDEFINED

An error occurred while attempting to retrieve the JavaScript undefined value.

ERR_NAPI_TSFN_START_IDLE_LOOP

On the main thread, values are removed from the queue associated with the thread-safe function in an idle loop. This error indicates that an error has occurred when attempting to start the loop.

ERR_NAPI_TSFN_STOP_IDLE_LOOP

Once no more items are left in the queue, the idle loop must be suspended. This error indicates that the idle loop has failed to stop.

ERR_NO_CRYPTO

An attempt was made to use crypto features while Node.js was not compiled with OpenSSL crypto support.

ERR_NO_ICU

An attempt was made to use features that require ICU, but Node.js was not compiled with ICU support.

ERR_NO_LONGER_SUPPORTED

A Node.js API was called in an unsupported manner, such as Buffer.write(string, encoding, offset[, length]).

ERR_OUT_OF_RANGE

A given value is out of the accepted range.

ERR_REQUIRE_ESM

An attempt was made to require() an ES6 module.

ERR_SCRIPT_EXECUTION_INTERRUPTED

Script execution was interrupted by SIGINT (For example, when Ctrl+C was pressed).

ERR_SERVER_ALREADY_LISTEN

The server.listen() method was called while a net.Server was already listening. This applies to all instances of net.Server, including HTTP, HTTPS, and HTTP/2 Server instances.

ERR_SERVER_NOT_RUNNING

The server.close() method was called when a net.Server was not running. This applies to all instances of net.Server, including HTTP, HTTPS, and HTTP/2 Server instances.

ERR_SOCKET_ALREADY_BOUND

An attempt was made to bind a socket that has already been bound.

ERR_SOCKET_BAD_BUFFER_SIZE

An invalid (negative) size was passed for either the recvBufferSize or sendBufferSize options in dgram.createSocket().

ERR_SOCKET_BAD_PORT

An API function expecting a port >= 0 and < 65536 received an invalid value.

ERR_SOCKET_BAD_TYPE

An API function expecting a socket type (udp4 or udp6) received an invalid value.

ERR_SOCKET_BUFFER_SIZE

While using dgram.createSocket(), the size of the receive or send Buffer could not be determined.

ERR_SOCKET_CANNOT_SEND

Data could be sent on a socket.

ERR_SOCKET_CLOSED

An attempt was made to operate on an already closed socket.

ERR_SOCKET_DGRAM_NOT_RUNNING

A call was made and the UDP subsystem was not running.

ERR_STREAM_CANNOT_PIPE

An attempt was made to call stream.pipe() on a Writable stream.

ERR_STREAM_DESTROYED

A stream method was called that cannot complete because the stream was destroyed using stream.destroy().

ERR_STREAM_NULL_VALUES

An attempt was made to call stream.write() with a null chunk.

ERR_STREAM_PREMATURE_CLOSE

An error returned by stream.finished() and stream.pipeline(), when a stream or a pipeline ends non gracefully with no explicit error.

ERR_STREAM_PUSH_AFTER_EOF

An attempt was made to call stream.push() after a null(EOF) had been pushed to the stream.

ERR_STREAM_UNSHIFT_AFTER_END_EVENT

An attempt was made to call stream.unshift() after the 'end' event was emitted.

ERR_STREAM_WRAP

Prevents an abort if a string decoder was set on the Socket or if the decoder is in objectMode.

const Socket = require('net').Socket;
const instance = new Socket();

instance.setEncoding('utf8');

ERR_STREAM_WRITE_AFTER_END

An attempt was made to call stream.write() after stream.end() has been called.

ERR_STRING_TOO_LONG

An attempt has been made to create a string longer than the maximum allowed length.

ERR_SYSTEM_ERROR

An unspecified or non-specific system error has occurred within the Node.js process. The error object will have an err.info object property with additional details.

ERR_TLS_CERT_ALTNAME_INVALID

While using TLS, the hostname/IP of the peer did not match any of the subjectAltNames in its certificate.

ERR_TLS_DH_PARAM_SIZE

While using TLS, the parameter offered for the Diffie-Hellman (DH) key-agreement protocol is too small. By default, the key length must be greater than or equal to 1024 bits to avoid vulnerabilities, even though it is strongly recommended to use 2048 bits or larger for stronger security.

ERR_TLS_HANDSHAKE_TIMEOUT

A TLS/SSL handshake timed out. In this case, the server must also abort the connection.

ERR_TLS_INVALID_PROTOCOL_VERSION

Valid TLS protocol versions are 'TLSv1', 'TLSv1.1', or 'TLSv1.2'.

ERR_TLS_PROTOCOL_VERSION_CONFLICT

Attempting to set a TLS protocol minVersion or maxVersion conflicts with an attempt to set the secureProtocol explicitly. Use one mechanism or the other.

ERR_TLS_RENEGOTIATE

An attempt to renegotiate the TLS session failed.

ERR_TLS_RENEGOTIATION_DISABLED

An attempt was made to renegotiate TLS on a socket instance with TLS disabled.

ERR_TLS_REQUIRED_SERVER_NAME

While using TLS, the server.addContext() method was called without providing a hostname in the first parameter.

ERR_TLS_SESSION_ATTACK

An excessive amount of TLS renegotiations is detected, which is a potential vector for denial-of-service attacks.

ERR_TLS_SNI_FROM_SERVER

An attempt was made to issue Server Name Indication from a TLS server-side socket, which is only valid from a client.

ERR_TRACE_EVENTS_CATEGORY_REQUIRED

The trace_events.createTracing() method requires at least one trace event category.

ERR_TRACE_EVENTS_UNAVAILABLE

The trace_events module could not be loaded because Node.js was compiled with the --without-v8-platform flag.

ERR_TRANSFERRING_EXTERNALIZED_SHAREDARRAYBUFFER

A SharedArrayBuffer whose memory is not managed by the JavaScript engine or by Node.js was encountered during serialization. Such a SharedArrayBuffer cannot be serialized.

This can only happen when native addons create SharedArrayBuffers in "externalized" mode, or put existing SharedArrayBuffer into externalized mode.

ERR_TRANSFORM_ALREADY_TRANSFORMING

A Transform stream finished while it was still transforming.

ERR_TRANSFORM_WITH_LENGTH_0

A Transform stream finished with data still in the write buffer.

ERR_TTY_INIT_FAILED

The initialization of a TTY failed due to a system error.

ERR_UNCAUGHT_EXCEPTION_CAPTURE_ALREADY_SET

process.setUncaughtExceptionCaptureCallback() was called twice, without first resetting the callback to null.

This error is designed to prevent accidentally overwriting a callback registered from another module.

ERR_UNESCAPED_CHARACTERS

A string that contained unescaped characters was received.

ERR_UNHANDLED_ERROR

An unhandled error occurred (for instance, when an 'error' event is emitted by an EventEmitter but an 'error' handler is not registered).

ERR_UNKNOWN_BUILTIN_MODULE

Used to identify a specific kind of internal Node.js error that should not typically be triggered by user code. Instances of this error point to an internal bug within the Node.js binary itself.

ERR_UNKNOWN_ENCODING

An invalid or unknown encoding option was passed to an API.

ERR_UNKNOWN_FILE_EXTENSION

An attempt was made to load a module with an unknown or unsupported file extension.

ERR_UNKNOWN_MODULE_FORMAT

An attempt was made to load a module with an unknown or unsupported format.

ERR_UNKNOWN_SIGNAL

An invalid or unknown process signal was passed to an API expecting a valid signal (such as subprocess.kill()).

ERR_UNKNOWN_STDIN_TYPE

An attempt was made to launch a Node.js process with an unknown stdin file type. This error is usually an indication of a bug within Node.js itself, although it is possible for user code to trigger it.

ERR_UNKNOWN_STREAM_TYPE

An attempt was made to launch a Node.js process with an unknown stdout or stderr file type. This error is usually an indication of a bug within Node.js itself, although it is possible for user code to trigger it.

ERR_V8BREAKITERATOR

The V8 BreakIterator API was used but the full ICU data set is not installed.

ERR_VALID_PERFORMANCE_ENTRY_TYPE

While using the Performance Timing API (perf_hooks), no valid performance entry types were found.

ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING

A dynamic import callback was not specified.

ERR_VM_MODULE_ALREADY_LINKED

The module attempted to be linked is not eligible for linking, because of one of the following reasons:

• It has already been linked (linkingStatus is 'linked')
• It is being linked (linkingStatus is 'linking')
• Linking has failed for this module (linkingStatus is 'errored')

ERR_VM_MODULE_DIFFERENT_CONTEXT

The module being returned from the linker function is from a different context than the parent module. Linked modules must share the same context.

ERR_VM_MODULE_LINKING_ERRORED

The linker function returned a module for which linking has failed.

ERR_VM_MODULE_NOT_LINKED

The module must be successfully linked before instantiation.

ERR_VM_MODULE_NOT_MODULE

The fulfilled value of a linking promise is not a vm.SourceTextModule object.

ERR_VM_MODULE_STATUS

The current module's status does not allow for this operation. The specific meaning of the error depends on the specific function.

ERR_WORKER_PATH

The path for the main script of a worker is neither an absolute path nor a relative path starting with ./ or ../.

ERR_WORKER_UNSERIALIZABLE_ERROR

All attempts at serializing an uncaught exception from a worker thread failed.

ERR_WORKER_UNSUPPORTED_EXTENSION

The pathname used for the main script of a worker has an unknown file extension.

ERR_ZLIB_INITIALIZATION_FAILED

Creation of a zlib object failed due to incorrect configuration.

HPE_HEADER_OVERFLOW

Too much HTTP header data was received. In order to protect against malicious or malconfigured clients, if more than 8KB of HTTP header data is received then HTTP parsing will abort without a request or response object being created, and an Error with this code will be emitted.

MODULE_NOT_FOUND

A module file could not be resolved while attempting a require() or import operation.

Legacy Node.js Error Codes

ERR_HTTP2_FRAME_ERROR

Used when a failure occurs sending an individual frame on the HTTP/2 session.

ERR_HTTP2_HEADERS_OBJECT

Used when an HTTP/2 Headers Object is expected.

ERR_HTTP2_HEADER_REQUIRED

Used when a required header is missing in an HTTP/2 message.

ERR_HTTP2_INFO_HEADERS_AFTER_RESPOND

HTTP/2 informational headers must only be sent prior to calling the Http2Stream.prototype.respond() method.

ERR_HTTP2_STREAM_CLOSED

Used when an action has been performed on an HTTP/2 Stream that has already been closed.

ERR_HTTP_INVALID_CHAR

Used when an invalid character is found in an HTTP response status message (reason phrase).

ERR_NAPI_CONS_PROTOTYPE_OBJECT

Used by the N-API when Constructor.prototype is not an object.

ERR_OUTOFMEMORY

Used generically to identify that an operation caused an out of memory condition.

ERR_PARSE_HISTORY_DATA

The repl module was unable to parse data from the REPL history file.

ERR_STDERR_CLOSE

An attempt was made to close the process.stderr stream. By design, Node.js does not allow stdout or stderr streams to be closed by user code.

ERR_STDOUT_CLOSE

An attempt was made to close the process.stdout stream. By design, Node.js does not allow stdout or stderr streams to be closed by user code.

ERR_STREAM_READ_NOT_IMPLEMENTED

Used when an attempt is made to use a readable stream that has not implemented readable._read().

ERR_TLS_RENEGOTIATION_FAILED

Used when a TLS renegotiation request has failed in a non-specific way.

ERR_UNKNOWN_BUILTIN_MODULE

The 'ERR_UNKNOWN_BUILTIN_MODULE' error code is used to identify a specific kind of internal Node.js error that should not typically be triggered by user code. Instances of this error point to an internal bug within the Node.js binary itself.

ERR_VALUE_OUT_OF_RANGE

Used when a given value is out of the accepted range.

ERR_ZLIB_BINDING_CLOSED

Used when an attempt is made to use a zlib object after it has already been closed.

Other error codes

These errors have never been released, but had been present on master between releases.

ERR_FS_WATCHER_ALREADY_STARTED

An attempt was made to start a watcher returned by fs.watch() that has already been started.

ERR_FS_WATCHER_NOT_STARTED

An attempt was made to initiate operations on a watcher returned by fs.watch() that has not yet been started.

ERR_HTTP2_ALREADY_SHUTDOWN

Occurs with multiple attempts to shutdown an HTTP/2 session.

ERR_HTTP2_ERROR

A non-specific HTTP/2 error has occurred.

ERR_INVALID_REPL_HISTORY

Used in the repl in case the old history file is used and an error occurred while trying to read and parse it.

ERR_MISSING_DYNAMIC_INSTANTIATE_HOOK

Used when an ES6 module loader hook specifies format: 'dynamic' but does not provide a dynamicInstantiate hook.

ERR_STREAM_HAS_STRINGDECODER

Used to prevent an abort if a string decoder was set on the Socket.

const Socket = require('net').Socket;
const instance = new Socket();

instance.setEncoding('utf8');

ERR_STRING_TOO_LARGE

An attempt has been made to create a string larger than the maximum allowed size.