Node.js v26.2.0 documentation

Command-line API#

Node.js comes with a variety of CLI options. These options expose built-in debugging, multiple ways to execute scripts, and other helpful runtime options.

Synopsis#

node [options] [V8 options] [<program-entry-point> | -e "script" | -] [--] [arguments]

node inspect [<program-entry-point> | -e "script" | <host>:<port>] …

node --v8-options

Execute without arguments to start the REPL.

Program entry point#

The program entry point is a specifier-like string. If the string is not an absolute path, it's resolved as a relative path from the current working directory. That entry point string is then resolved as if it's been requested by require() from the current working directory. If no corresponding file is found, an error is thrown.

By default, the resolved path is also loaded as if it's been requested by require(), unless one of the conditions below apply—then it's loaded as if it's been requested by import():

• The program was started with a command-line flag that forces the entry point to be loaded with ECMAScript module loader, such as --import.
• The file has an .mjs, .mts or .wasm extension.
• The file does not have a .cjs extension, and the nearest parent package.json file contains a top-level "type" field with a value of "module".

Options#

Underscores instead of dashes are now allowed for Node.js options as well, in addition to V8 options.

All options, including V8 options, allow words to be separated by both dashes (-) or underscores (_). For example, --pending-deprecation is equivalent to --pending_deprecation.

-#

--#

--abort-on-uncaught-exception#

Aborting instead of exiting causes a core file to be generated for post-mortem analysis using a debugger (such as lldb, gdb, and mdb).

--allow-addons#

When using the Permission Model, the process will not be able to use native addons by default. Attempts to do so will throw an ERR_DLOPEN_DISABLED unless the user explicitly passes the --allow-addons flag when starting Node.js.

// Attempt to require an native addon
require('nodejs-addon-example');
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$ node --permission --allow-fs-read=* index.js
node:internal/modules/cjs/loader:1319
  return process.dlopen(module, path.toNamespacedPath(filename));
                 ^

Error: Cannot load native addon because loading addons is disabled.
    at Module._extensions..node (node:internal/modules/cjs/loader:1319:18)
    at Module.load (node:internal/modules/cjs/loader:1091:32)
    at Module._load (node:internal/modules/cjs/loader:938:12)
    at Module.require (node:internal/modules/cjs/loader:1115:19)
    at require (node:internal/modules/helpers:130:18)
    at Object.<anonymous> (/home/index.js:1:15)
    at Module._compile (node:internal/modules/cjs/loader:1233:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1287:10)
    at Module.load (node:internal/modules/cjs/loader:1091:32)
    at Module._load (node:internal/modules/cjs/loader:938:12) {
  code: 'ERR_DLOPEN_DISABLED'
}
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--allow-child-process#

When spawning process with the permission model enabled. The flags are inherit to the child Node.js process through NODE_OPTIONS environment variable.

When using the Permission Model, the process will not be able to spawn any child process by default. Attempts to do so will throw an ERR_ACCESS_DENIED unless the user explicitly passes the --allow-child-process flag when starting Node.js.

Example:

const childProcess = require('node:child_process');
// Attempt to bypass the permission
childProcess.spawn('node', ['-e', 'require("fs").writeFileSync("/new-file", "example")']);
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$ node --permission --allow-fs-read=* index.js
node:internal/child_process:388
  const err = this._handle.spawn(options);
                           ^
Error: Access to this API has been restricted
    at ChildProcess.spawn (node:internal/child_process:388:28)
    at node:internal/main/run_main_module:17:47 {
  code: 'ERR_ACCESS_DENIED',
  permission: 'ChildProcess'
}
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The child_process.fork() API inherits the execution arguments from the parent process. This means that if Node.js is started with the Permission Model enabled and the --allow-child-process flag is set, any child process created using child_process.fork() will automatically receive all relevant Permission Model flags.

--allow-ffi#

When using the Permission Model, the process will not be able to use FFI APIs by default. Attempts to use FFI APIs will throw an ERR_ACCESS_DENIED exception unless the user explicitly passes the --allow-ffi flag when starting Node.js. The node:ffi module also requires the --experimental-ffi flag and is only available in builds with FFI support.

const { DynamicLibrary } = require('node:ffi');
const lib = new DynamicLibrary('mylib.so');
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$ node --permission --experimental-ffi index.js
Error: Access to this API has been restricted. Use --allow-ffi to manage permissions.
    at node:internal/main/run_main_module:17:47 {
  code: 'ERR_ACCESS_DENIED',
  permission: 'FFI'
}
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--allow-fs-read#

Paths delimited by comma (,) are no longer allowed.

This flag configures file system read permissions using the Permission Model.

The valid arguments for the --allow-fs-read flag are:

• * - To allow all FileSystemRead operations.
• Multiple paths can be allowed using multiple --allow-fs-read flags. Example --allow-fs-read=/folder1/ --allow-fs-read=/folder1/

Examples can be found in the File System Permissions documentation.

$ node --permission -r custom-require.js -r custom-require-2.js index.js
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• The custom-require.js, custom-require-2.js, and index.js will be by default in the allowed read list.

process.permission.has('fs.read', 'index.js'); // true
process.permission.has('fs.read', 'custom-require.js'); // true
process.permission.has('fs.read', 'custom-require-2.js'); // true
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--allow-fs-write#

Paths delimited by comma (,) are no longer allowed.

This flag configures file system write permissions using the Permission Model.

The valid arguments for the --allow-fs-write flag are:

• * - To allow all FileSystemWrite operations.
• Multiple paths can be allowed using multiple --allow-fs-write flags. Example --allow-fs-write=/folder1/ --allow-fs-write=/folder1/

Paths delimited by comma (,) are no longer allowed. When passing a single flag with a comma a warning will be displayed.

--allow-inspector#

When using the Permission Model, the process will not be able to connect through inspector protocol.

Attempts to do so will throw an ERR_ACCESS_DENIED unless the user explicitly passes the --allow-inspector flag when starting Node.js.

const { Session } = require('node:inspector/promises');

const session = new Session();
session.connect();
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$ node --permission index.js
Error: connect ERR_ACCESS_DENIED Access to this API has been restricted. Use --allow-inspector to manage permissions.
  code: 'ERR_ACCESS_DENIED',
}
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--allow-net#

When using the Permission Model, the process will not be able to access network by default. Attempts to do so will throw an ERR_ACCESS_DENIED unless the user explicitly passes the --allow-net flag when starting Node.js.

const http = require('node:http');
// Attempt to bypass the permission
const req = http.get('http://example.com', () => {});

req.on('error', (err) => {
  console.log('err', err);
});
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$ node --permission index.js
Error: connect ERR_ACCESS_DENIED Access to this API has been restricted. Use --allow-net to manage permissions.
  code: 'ERR_ACCESS_DENIED',
}
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--allow-wasi#

When using the Permission Model, the process will not be capable of creating any WASI instances by default. For security reasons, the call will throw an ERR_ACCESS_DENIED unless the user explicitly passes the flag --allow-wasi in the main Node.js process.

const { WASI } = require('node:wasi');
// Attempt to bypass the permission
new WASI({
  version: 'preview1',
  // Attempt to mount the whole filesystem
  preopens: {
    '/': '/',
  },
});
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$ node --permission --allow-fs-read=* index.js

Error: Access to this API has been restricted
    at node:internal/main/run_main_module:30:49 {
  code: 'ERR_ACCESS_DENIED',
  permission: 'WASI',
}
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--allow-worker#

When using the Permission Model, the process will not be able to create any worker threads by default. For security reasons, the call will throw an ERR_ACCESS_DENIED unless the user explicitly pass the flag --allow-worker in the main Node.js process.

const { Worker } = require('node:worker_threads');
// Attempt to bypass the permission
new Worker(__filename);
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$ node --permission --allow-fs-read=* index.js

Error: Access to this API has been restricted
    at node:internal/main/run_main_module:17:47 {
  code: 'ERR_ACCESS_DENIED',
  permission: 'WorkerThreads'
}
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--build-sea=config#

Generates a single executable application from a JSON configuration file. The argument must be a path to the configuration file. If the path is not absolute, it is resolved relative to the current working directory.

--build-snapshot#

The snapshot building process is no longer experimental.

Generates a snapshot blob when the process exits and writes it to disk, which can be loaded later with --snapshot-blob.

When building the snapshot, if --snapshot-blob is not specified, the generated blob will be written, by default, to snapshot.blob in the current working directory. Otherwise it will be written to the path specified by --snapshot-blob.

$ echo "globalThis.foo = 'I am from the snapshot'" > snapshot.js

# Run snapshot.js to initialize the application and snapshot the
# state of it into snapshot.blob.
$ node --snapshot-blob snapshot.blob --build-snapshot snapshot.js

$ echo "console.log(globalThis.foo)" > index.js

# Load the generated snapshot and start the application from index.js.
$ node --snapshot-blob snapshot.blob index.js
I am from the snapshot
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The v8.startupSnapshot API can be used to specify an entry point at snapshot building time, thus avoiding the need of an additional entry script at deserialization time:

$ echo "require('v8').startupSnapshot.setDeserializeMainFunction(() => console.log('I am from the snapshot'))" > snapshot.js
$ node --snapshot-blob snapshot.blob --build-snapshot snapshot.js
$ node --snapshot-blob snapshot.blob
I am from the snapshot
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For more information, check out the v8.startupSnapshot API documentation.

The snapshot currently only supports loding a single entrypoint during the snapshot building process, which can load built-in modules, but not additional user-land modules. Users can bundle their applications into a single script with their bundler of choice before building a snapshot.

--build-snapshot-config#

The snapshot building process is no longer experimental.

Specifies the path to a JSON configuration file which configures snapshot creation behavior.

The following options are currently supported:

• builder <string> Required. Provides the name to the script that is executed before building the snapshot, as if --build-snapshot had been passed with builder as the main script name.
• withoutCodeCache <boolean> Optional. Including the code cache reduces the time spent on compiling functions included in the snapshot at the expense of a bigger snapshot size and potentially breaking portability of the snapshot.

-c, --check#

The --require option is now supported when checking a file.

--completion-bash#

node --completion-bash > node_bash_completion
source node_bash_completion
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-C condition, --conditions=condition#

The flag is no longer experimental.

Provide custom conditional exports resolution conditions.

Any number of custom string condition names are permitted.

The default Node.js conditions of "node", "default", "import", and "require" will always apply as defined.

node -C development app.js
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--cpu-prof#

The --cpu-prof flags are now stable.

Starts the V8 CPU profiler on start up, and writes the CPU profile to disk before exit.

If --cpu-prof-dir is not specified, the generated profile is placed in the current working directory.

If --cpu-prof-name is not specified, the generated profile is named CPU.${yyyymmdd}.${hhmmss}.${pid}.${tid}.${seq}.cpuprofile.

$ node --cpu-prof index.js
$ ls *.cpuprofile
CPU.20190409.202950.15293.0.0.cpuprofile
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• ${pid} — the current process ID

$ node --cpu-prof --cpu-prof-name 'CPU.${pid}.cpuprofile' index.js
$ ls *.cpuprofile
CPU.15293.cpuprofile
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--cpu-prof-dir#

The --cpu-prof flags are now stable.

Specify the directory where the CPU profiles generated by --cpu-prof will be placed.

--cpu-prof-interval#

The --cpu-prof flags are now stable.

--cpu-prof-name#

The --cpu-prof flags are now stable.

--diagnostic-dir=directory#

Set the directory to which all diagnostic output files are written. Defaults to current working directory.

• --cpu-prof-dir
• --heap-prof-dir
• --redirect-warnings

--disable-proto=mode#

--disable-sigusr1#

The option is no longer experimental.

--disable-warning=code-or-type#

Disable specific process warnings by code or type.

Warnings emitted from process.emitWarning() may contain a code and a type. This option will not-emit warnings that have a matching code or type.

List of deprecation warnings.

The Node.js core warning types are: DeprecationWarning and ExperimentalWarning

For example, the following script will not emit DEP0025 require('node:sys') when executed with node --disable-warning=DEP0025:

import sys from 'node:sys';
const sys = require('node:sys');
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import sys from 'node:sys';
import vm from 'node:vm';

vm.measureMemory();
const sys = require('node:sys');
const vm = require('node:vm');

vm.measureMemory();
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--disable-wasm-trap-handler#

Node.js now automatically disables the trap handler when there is not enough virtual memory available at startup to allocate one cage.

Node.js enables V8's trap-handler-based WebAssembly bound checks on 64-bit platforms, which significantly improves WebAssembly performance by eliminating the need for inline bound checks. This optimization requires allocating a large virtual memory cage per WebAssembly memory instance (currently typically 8GB for 32-bit WebAssembly memory, 16GB for 64-bit WebAssembly memory) to trap out-of-bound accesses. On most 64-bit platforms, the virtual memory address space is usually large enough (around 128TB) to accommodate typical WebAssembly usages, but if the machine has manual limits on virtual memory (e.g. through ulimit -v), WebAssembly memory allocation is more likely to fail with WebAssembly.Memory(): could not allocate memory.

At startup, Node.js automatically checks whether there is enough virtual memory available to allocate at least one cage, and if not, the trap-handler optimization is automatically disabled so that WebAssembly can still run using inline bound checks (with less optimal performance). But if the application needs to create many WebAssembly memory instances and the machine still configures a relatively high limit on virtual memory, allocation of WebAssembly memory instances may still fail more quickly than expected due to the raised virtual memory usage.

--disallow-code-generation-from-strings#

--dns-result-order=order#

Changed default value to verbatim.

Set the default value of order in dns.lookup() and dnsPromises.lookup(). The value could be:

• ipv4first: sets default order to ipv4first.
• ipv6first: sets default order to ipv6first.
• verbatim: sets default order to verbatim.

--enable-fips#

--enable-source-maps#

This API is no longer experimental.

Enable Source Map support for stack traces.

When using a transpiler, such as TypeScript, stack traces thrown by an application reference the transpiled code, not the original source position. --enable-source-maps enables caching of Source Maps and makes a best effort to report stack traces relative to the original source file.

Overriding Error.prepareStackTrace may prevent --enable-source-maps from modifying the stack trace. Call and return the results of the original Error.prepareStackTrace in the overriding function to modify the stack trace with source maps.

const originalPrepareStackTrace = Error.prepareStackTrace;
Error.prepareStackTrace = (error, trace) => {
  // Modify error and trace and format stack trace with
  // original Error.prepareStackTrace.
  return originalPrepareStackTrace(error, trace);
};
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--entry-url#

When present, Node.js will interpret the entry point as a URL, rather than a path.

Follows ECMAScript module resolution rules.

node --entry-url 'file:///path/to/file.js?queryparams=work#and-hashes-too'
node --entry-url 'file.ts?query#hash'
node --entry-url 'data:text/javascript,console.log("Hello")'
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--env-file-if-exists=file#

The --env-file-if-exists flag is no longer experimental.

--env-file=file#

Add support to multi-line values.

Loads environment variables from a file relative to the current directory, making them available to applications on process.env. The environment variables which configure Node.js, such as NODE_OPTIONS, are parsed and applied. If the same variable is defined in the environment and in the file, the value from the environment takes precedence.

You can pass multiple --env-file arguments. Subsequent files override pre-existing variables defined in previous files.

An error is thrown if the file does not exist.

node --env-file=.env --env-file=.development.env index.js
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The format of the file should be one line per key-value pair of environment variable name and value separated by =:

PORT=3000
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Any text after a # is treated as a comment:

# This is a comment
PORT=3000 # This is also a comment
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Values can start and end with the following quotes: `, " or '. They are omitted from the values.

USERNAME="nodejs" # will result in `nodejs` as the value.
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Multi-line values are supported:

MULTI_LINE="THIS IS
A MULTILINE"
# will result in `THIS IS\nA MULTILINE` as the value.
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Export keyword before a key is ignored:

export USERNAME="nodejs" # will result in `nodejs` as the value.
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-e, --eval "script"#

Built-in libraries are now available as predefined variables.

Evaluate the following argument as JavaScript. The modules which are predefined in the REPL can also be used in script.

If script starts with -, pass it using = (for example, node --print --eval=-42) so it is parsed as the value of --eval.

On Windows, using cmd.exe a single quote will not work correctly because it only recognizes double " for quoting. In Powershell or Git bash, both ' and " are usable.

--experimental-addon-modules#

--experimental-config-file=path, --experimental-config-file#

If present, Node.js will look for a configuration file at the specified path. If the path is not specified, Node.js will look for a node.config.json file in the current working directory. To specify a custom path, use the --experimental-config-file=path form. The space-separated --experimental-config-file path form is not supported. The alias --experimental-default-config-file is equivalent to --experimental-config-file without an argument. Node.js will read the configuration file and apply the settings. The configuration file should be a JSON file with the following structure. vX.Y.Z in the $schema must be replaced with the version of Node.js you are using or latest-vX.x for the latest version of that major release line.

{
  "$schema": "https://nodejs.org/dist/vX.Y.Z/docs/node-config-schema.json",
  "nodeOptions": {
    "import": [
      "amaro/strip"
    ],
    "watch-path": "src",
    "watch-preserve-output": true
  },
  "test": {
    "test-isolation": "process"
  },
  "watch": {
    "watch-preserve-output": true
  }
}
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The configuration file supports namespace-specific options:

• The nodeOptions field contains CLI flags that are allowed in NODE_OPTIONS.

• Namespace fields like test, watch, and permission contain configuration specific to that subsystem.

The configuration file can target a specific Node.js major version with nodeVersion:

{
  "nodeVersion": 25,
  "nodeOptions": {
    "watch-path": "src"
  }
}
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To keep multiple version-specific configurations in the same file, use the configs array. Node.js will use the first entry whose nodeVersion matches the current Node.js major version:

{
  "$schema": "https://nodejs.org/dist/latest-v26.x/docs/node-config-schema.json",
  "configs": [
    {
      "nodeVersion": 25,
      "config": {
        "$schema": "https://nodejs.org/dist/latest-v25.x/docs/node-config-schema.json",
        "nodeOptions": {
          "watch-path": "src"
        }
      }
    }
  ]
}
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When configs is used, the top level may only contain $schema and configs. Each configs item must define an integer nodeVersion and an object config. A single top-level config does not require nodeVersion, but if present it must match the current Node.js major version.

When a namespace is present in the configuration file, Node.js automatically enables the corresponding flag (e.g., --test, --watch, --permission). This allows you to configure subsystem-specific options without explicitly passing the flag on the command line.

For example:

{
  "test": {
    "test-isolation": "process"
  }
}
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is equivalent to:

node --test --test-isolation=process
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To disable the automatic flag while still using namespace options, you can explicitly set the flag to false within the namespace:

{
  "test": {
    "test": false,
    "test-isolation": "process"
  }
}
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No-op flags are not supported. Not all V8 flags are currently supported.

It is possible to use the official JSON schema to validate the configuration file, which may vary depending on the Node.js version. Each key in the configuration file corresponds to a flag that can be passed as a command-line argument. The value of the key is the value that would be passed to the flag.

For example, the configuration file above is equivalent to the following command-line arguments:

node --import amaro/strip --watch-path=src --watch-preserve-output --test-isolation=process
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The priority in configuration is as follows:

1. NODE_OPTIONS and command-line options
2. Dotenv NODE_OPTIONS
3. Configuration file

Values in the configuration file will not override the values in the environment variables, command-line options, or the NODE_OPTIONS env file parsed by the --env-file flag.

Keys cannot be duplicated within the same or different namespaces.

The configuration parser will throw an error if the configuration file contains unknown keys or keys that cannot be used in a namespace.

--experimental-default-config-file#

--experimental-eventsource#

--experimental-ffi#

Enable the experimental node:ffi module.

--experimental-import-meta-resolve#

synchronous import.meta.resolve made available by default, with the flag retained for enabling the experimental second argument as previously supported.

Enable experimental import.meta.resolve() parent URL support, which allows passing a second parentURL argument for contextual resolution.

--experimental-inspector-network-resource#

--experimental-loader=module#

This flag was renamed from --loader to --experimental-loader.

This flag is discouraged and may be removed in a future version of Node.js. Please use --import with register() instead.

Specify the module containing exported asynchronous module customization hooks. module may be any string accepted as an import specifier.

--experimental-network-inspection#

--experimental-print-required-tla#

--experimental-quic#

--experimental-sea-config#

--experimental-shadow-realm#

--experimental-storage-inspection#

--experimental-stream-iter#

--experimental-test-coverage#

This option can be used with --test.

--experimental-test-module-mocks#

Using this feature with the permission model enabled requires passing --allow-worker.

Enable module mocking in the test runner.

--experimental-test-tag-filter=<tag>#

Run only tests whose tag set contains <tag>. Tests declare tags via the tags option on test(), it(), suite(), or describe(); tags inherit from suites to nested tests by union. Filtering is case-insensitive.

--experimental-vm-modules#

--experimental-wasi-unstable-preview1#

changed from --experimental-wasi-unstable-preview0 to --experimental-wasi-unstable-preview1.

--experimental-worker-inspection#

--expose-gc#

if (globalThis.gc) {
  globalThis.gc();
}
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--force-context-aware#

--force-fips#

--force-node-api-uncaught-exceptions-policy#

Enforces uncaughtException event on Node-API asynchronous callbacks.

--frozen-intrinsics#

Enable experimental frozen intrinsics like Array and Object.

Only the root context is supported. There is no guarantee that globalThis.Array is indeed the default intrinsic reference. Code may break under this flag.

--heap-prof#

The --heap-prof flags are now stable.

Starts the V8 heap profiler on start up, and writes the heap profile to disk before exit.

If --heap-prof-dir is not specified, the generated profile is placed in the current working directory.

$ node --heap-prof index.js
$ ls *.heapprofile
Heap.20190409.202950.15293.0.001.heapprofile
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--heap-prof-dir#

The --heap-prof flags are now stable.

Specify the directory where the heap profiles generated by --heap-prof will be placed.

--heap-prof-interval#

The --heap-prof flags are now stable.

--heap-prof-name#

The --heap-prof flags are now stable.

--heapsnapshot-near-heap-limit=max_count#

The flag is no longer experimental.

Writes a V8 heap snapshot to disk when the V8 heap usage is approaching the heap limit. count should be a non-negative integer (in which case Node.js will write no more than max_count snapshots to disk).

When generating snapshots, garbage collection may be triggered and bring the heap usage down. Therefore multiple snapshots may be written to disk before the Node.js instance finally runs out of memory. These heap snapshots can be compared to determine what objects are being allocated during the time consecutive snapshots are taken. It's not guaranteed that Node.js will write exactly max_count snapshots to disk, but it will try its best to generate at least one and up to max_count snapshots before the Node.js instance runs out of memory when max_count is greater than 0.

$ node --max-old-space-size=100 --heapsnapshot-near-heap-limit=3 index.js
Wrote snapshot to Heap.20200430.100036.49580.0.001.heapsnapshot
Wrote snapshot to Heap.20200430.100037.49580.0.002.heapsnapshot
Wrote snapshot to Heap.20200430.100038.49580.0.003.heapsnapshot

<--- Last few GCs --->

[49580:0x110000000]     4826 ms: Mark-sweep 130.6 (147.8) -> 130.5 (147.8) MB, 27.4 / 0.0 ms  (average mu = 0.126, current mu = 0.034) allocation failure scavenge might not succeed
[49580:0x110000000]     4845 ms: Mark-sweep 130.6 (147.8) -> 130.6 (147.8) MB, 18.8 / 0.0 ms  (average mu = 0.088, current mu = 0.031) allocation failure scavenge might not succeed


<--- JS stacktrace --->

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory
....
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--heapsnapshot-signal=signal#

$ node --heapsnapshot-signal=SIGUSR2 index.js &
$ ps aux
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
node         1  5.5  6.1 787252 247004 ?       Ssl  16:43   0:02 node --heapsnapshot-signal=SIGUSR2 index.js
$ kill -USR2 1
$ ls
Heap.20190718.133405.15554.0.001.heapsnapshot
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-h, --help#

--icu-data-dir=file#

--import=module#

Preload the specified module at startup. If the flag is provided several times, each module will be executed sequentially in the order they appear, starting with the ones provided in NODE_OPTIONS.

Follows ECMAScript module resolution rules. Use --require to load a CommonJS module. Modules preloaded with --require will run before modules preloaded with --import.

--input-type=type#

ESM syntax detection is enabled by default.

This configures Node.js to interpret --eval or STDIN input as CommonJS or as an ES module. Valid values are "commonjs", "module", "module-typescript" and "commonjs-typescript". The "-typescript" values are not available with the flag --no-strip-types. The default is no value, or "commonjs" if --no-experimental-detect-module is passed.

If --input-type is not provided, Node.js will try to detect the syntax with the following steps:

1. Run the input as CommonJS.
2. If step 1 fails, run the input as an ES module.
3. If step 2 fails with a SyntaxError, strip the types.
4. If step 3 fails with an error code ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX or ERR_INVALID_TYPESCRIPT_SYNTAX, throw the error from step 2, including the TypeScript error in the message, else run as CommonJS.
5. If step 4 fails, run the input as an ES module.

To avoid the delay of multiple syntax detection passes, the --input-type=type flag can be used to specify how the --eval input should be interpreted.

--insecure-http-parser#

Enable leniency flags on the HTTP parser. This may allow interoperability with non-conformant HTTP implementations.

When enabled, the parser will accept the following:

• Invalid HTTP headers values.
• Invalid HTTP versions.
• Allow message containing both Transfer-Encoding and Content-Length headers.
• Allow extra data after message when Connection: close is present.
• Allow extra transfer encodings after chunked has been provided.
• Allow \n to be used as token separator instead of \r\n.
• Allow \r\n not to be provided after a chunk.
• Allow spaces to be present after a chunk size and before \r\n.

--inspect-brk[=[host:]port]#

Activate inspector on host:port and break at start of user script. Default host:port is 127.0.0.1:9229. If port 0 is specified, a random available port will be used.

See V8 Inspector integration for Node.js for further explanation on Node.js debugger.

--inspect-port=[host:]port#

Set the host:port to be used when the inspector is activated. Useful when activating the inspector by sending the SIGUSR1 signal. Except when --disable-sigusr1 is passed.

Default host is 127.0.0.1. If port 0 is specified, a random available port will be used.

--inspect-publish-uid=stderr,http#

Specify ways of the inspector web socket url exposure.

--inspect-wait[=[host:]port]#

Activate inspector on host:port and wait for debugger to be attached. Default host:port is 127.0.0.1:9229. If port 0 is specified, a random available port will be used.

See V8 Inspector integration for Node.js for further explanation on Node.js debugger.

--inspect[=[host:]port]#

Activate inspector on host:port. Default is 127.0.0.1:9229. If port 0 is specified, a random available port will be used.

V8 inspector integration allows tools such as Chrome DevTools and IDEs to debug and profile Node.js instances. The tools attach to Node.js instances via a tcp port and communicate using the Chrome DevTools Protocol. See V8 Inspector integration for Node.js for further explanation on Node.js debugger.

Warning: binding inspector to a public IP:port combination is insecure#

Binding the inspector to a public IP (including 0.0.0.0) with an open port is insecure, as it allows external hosts to connect to the inspector and perform a remote code execution attack.

If specifying a host, make sure that either:

• The host is not accessible from public networks.
• A firewall disallows unwanted connections on the port.

More specifically, --inspect=0.0.0.0 is insecure if the port (9229 by default) is not firewall-protected.

-i, --interactive#

--jitless#

--localstorage-file=file#

--max-http-header-size=size#

Change maximum default size of HTTP headers from 8 KiB to 16 KiB.

--max-old-space-size-percentage=percentage#

Sets the maximum memory size of V8's old memory section as a percentage of available system memory. This flag takes precedence over --max-old-space-size when both are specified.

The percentage parameter must be a number greater than 0 and up to 100, representing the percentage of available system memory to allocate to the V8 heap.

# Using 50% of available system memory
node --max-old-space-size-percentage=50 index.js

# Using 75% of available system memory
node --max-old-space-size-percentage=75 index.js
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--napi-modules#

--network-family-autoselection-attempt-timeout#

--no-addons#

--no-async-context-frame#

--no-deprecation#

--no-experimental-detect-module#

Syntax detection is enabled by default.

--no-experimental-global-navigator#

--no-experimental-repl-await#

--no-experimental-require-module#

This is now false by default.

--no-experimental-sqlite#

SQLite is unflagged but still experimental.

--no-experimental-websocket#

--no-experimental-webstorage#

The feature is now enabled by default.

--no-extra-info-on-fatal-exception#

--no-force-async-hooks-checks#

--no-global-search-paths#

--no-network-family-autoselection#

The flag was renamed from --no-enable-network-family-autoselection to --no-network-family-autoselection. The old name can still work as an alias.

Disables the family autoselection algorithm unless connection options explicitly enables it.

--no-require-module#

This is now false by default.

Disable support for loading a synchronous ES module graph in require().

--no-strip-types#

Type stripping is enabled by default.

--no-warnings#

--node-memory-debug#

--openssl-config=file#

--openssl-legacy-provider#

--openssl-shared-config#

--pending-deprecation#

Emit pending deprecation warnings.

--permission#

Permission Model is now stable.

• File System - manageable through --allow-fs-read, --allow-fs-write flags
• Network - manageable through --allow-net flag
• Child Process - manageable through --allow-child-process flag
• Worker Threads - manageable through --allow-worker flag
• WASI - manageable through --allow-wasi flag
• Addons - manageable through --allow-addons flag
• FFI - manageable through --allow-ffi flag

--permission-audit#

--preserve-symlinks#

Instructs the module loader to preserve symbolic links when resolving and caching modules.

By default, when Node.js loads a module from a path that is symbolically linked to a different on-disk location, Node.js will dereference the link and use the actual on-disk "real path" of the module as both an identifier and as a root path to locate other dependency modules. In most cases, this default behavior is acceptable. However, when using symbolically linked peer dependencies, as illustrated in the example below, the default behavior causes an exception to be thrown if moduleA attempts to require moduleB as a peer dependency:

{appDir}
 ├── app
 │   ├── index.js
 │   └── node_modules
 │       ├── moduleA -> {appDir}/moduleA
 │       └── moduleB
 │           ├── index.js
 │           └── package.json
 └── moduleA
     ├── index.js
     └── package.json
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The --preserve-symlinks command-line flag instructs Node.js to use the symlink path for modules as opposed to the real path, allowing symbolically linked peer dependencies to be found.

Note, however, that using --preserve-symlinks can have other side effects. Specifically, symbolically linked native modules can fail to load if those are linked from more than one location in the dependency tree (Node.js would see those as two separate modules and would attempt to load the module multiple times, causing an exception to be thrown).

--preserve-symlinks-main#

Instructs the module loader to preserve symbolic links when resolving and caching the main module (require.main).

This flag exists so that the main module can be opted-in to the same behavior that --preserve-symlinks gives to all other imports; they are separate flags, however, for backward compatibility with older Node.js versions.

--preserve-symlinks-main does not imply --preserve-symlinks; use --preserve-symlinks-main in addition to --preserve-symlinks when it is not desirable to follow symlinks before resolving relative paths.

-p, --print "script"#

Built-in libraries are now available as predefined variables.

--prof#

--prof-process#

--redirect-warnings=file#

Write process warnings to the given file instead of printing to stderr. The file will be created if it does not exist, and will be appended to if it does. If an error occurs while attempting to write the warning to the file, the warning will be written to stderr instead.

--report-compact#

--report-dir=directory, --report-directory=directory#

Changed from --diagnostic-report-directory to --report-directory.

--report-exclude-env#

--report-exclude-network#

--report-filename=filename#

changed from --diagnostic-report-filename to --report-filename.

Name of the file to which the report will be written.

--report-on-fatalerror#

changed from --diagnostic-report-on-fatalerror to --report-on-fatalerror.

--report-on-signal#

changed from --diagnostic-report-on-signal to --report-on-signal.

--report-signal=signal#

changed from --diagnostic-report-signal to --report-signal.

--report-uncaught-exception#

changed from --diagnostic-report-uncaught-exception to --report-uncaught-exception.

-r, --require module#

This option also supports ECMAScript module.

Preload the specified module at startup.

Follows require()'s module resolution rules. module may be either a path to a file, or a node module name.

Modules preloaded with --require will run before modules preloaded with --import.

--run#

Traverses up to the root directory and finds a package.json file to run the command from, and updates PATH environment variable accordingly.

This runs a specified command from a package.json's "scripts" object. If a missing "command" is provided, it will list the available scripts.

--run will traverse up to the root directory and finds a package.json file to run the command from.

--run prepends ./node_modules/.bin for each ancestor of the current directory, to the PATH in order to execute the binaries from different folders where multiple node_modules directories are present, if ancestor-folder/node_modules/.bin is a directory.

--run executes the command in the directory containing the related package.json.

For example, the following command will run the test script of the package.json in the current folder:

$ node --run test
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$ node --run test -- --verbose
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Intentional limitations#

• Running pre or post scripts in addition to the specified script.
• Defining package manager-specific environment variables.

Environment variables#

• NODE_RUN_SCRIPT_NAME: The name of the script being run. For example, if --run is used to run test, the value of this variable will be test.
• NODE_RUN_PACKAGE_JSON_PATH: The path to the package.json that is being processed.

--secure-heap-min=n#

--secure-heap=n#

Initializes an OpenSSL secure heap of n bytes. When initialized, the secure heap is used for selected types of allocations within OpenSSL during key generation and other operations. This is useful, for instance, to prevent sensitive information from leaking due to pointer overruns or underruns.

The secure heap is a fixed size and cannot be resized at runtime so, if used, it is important to select a large enough heap to cover all application uses.

The heap size given must be a power of two. Any value less than 2 will disable the secure heap.

The secure heap is disabled by default.

The secure heap is not available on Windows.

--snapshot-blob=path#

When used with --build-snapshot, --snapshot-blob specifies the path where the generated snapshot blob is written to. If not specified, the generated blob is written to snapshot.blob in the current working directory.

When used without --build-snapshot, --snapshot-blob specifies the path to the blob that is used to restore the application state.

When loading a snapshot, Node.js checks that:

1. The version, architecture, and platform of the running Node.js binary are exactly the same as that of the binary that generates the snapshot.
2. The V8 flags and CPU features are compatible with that of the binary that generates the snapshot.

--test#

Test runner now supports running in watch mode.

--test-concurrency#

--test-coverage-branches=threshold#

--test-coverage-exclude#

Excludes specific files from code coverage using a glob pattern, which can match both absolute and relative file paths.

This option may be specified multiple times to exclude multiple glob patterns.

If both --test-coverage-exclude and --test-coverage-include are provided, files must meet both criteria to be included in the coverage report.

--test-coverage-functions=threshold#

--test-coverage-include#

Includes specific files in code coverage using a glob pattern, which can match both absolute and relative file paths.

This option may be specified multiple times to include multiple glob patterns.

--test-coverage-lines=threshold#

--test-force-exit#

--test-global-setup=module#

Specify a module that will be evaluated before all tests are executed and can be used to setup global state or fixtures for tests.

--test-isolation=mode#

This flag was renamed from --experimental-test-isolation to --test-isolation.

--test-name-pattern#

The test runner is now stable.

A regular expression that configures the test runner to only execute tests whose name matches the provided pattern. See the documentation on filtering tests by name for more details.

--test-only#

The test runner is now stable.

--test-random-seed#

Set the seed used to randomize test execution order. This applies to both test file execution order and queued tests within each file. Providing this flag enables randomization implicitly, even without --test-randomize.

The value must be an integer between 0 and 4294967295.

--test-randomize#

Randomize test execution order. This applies to both test file execution order and queued tests within each file. This can help detect tests that rely on shared state or execution order.

The seed used for randomization is printed in the test summary and can be reused with --test-random-seed.

For detailed behavior and examples, see randomizing tests execution order.

--test-reporter#

The test runner is now stable.

--test-reporter-destination#

The test runner is now stable.

--test-rerun-failures#

--test-shard#

Test suite shard to execute in a format of <index>/<total>, where

• index is a positive integer, index of divided parts.
• total is a positive integer, total of divided part.

This command will divide all tests files into total equal parts, and will run only those that happen to be in an index part.

node --test --test-shard=1/3
node --test --test-shard=2/3
node --test --test-shard=3/3
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--test-skip-pattern#

A regular expression that configures the test runner to skip tests whose name matches the provided pattern. See the documentation on filtering tests by name for more details.

--test-timeout#

--test-update-snapshots#

Snapshot testing is no longer experimental.

--throw-deprecation#

--title=title#

--tls-cipher-list=list#

--tls-keylog=file#

--tls-max-v1.2#

--tls-max-v1.3#

--tls-min-v1.0#

--tls-min-v1.1#

--tls-min-v1.2#

--tls-min-v1.3#

--trace-deprecation#

--trace-env#

Print information about any access to environment variables done in the current Node.js instance to stderr, including:

• The environment variable reads that Node.js does internally.
• Writes in the form of process.env.KEY = "SOME VALUE".
• Reads in the form of process.env.KEY.
• Definitions in the form of Object.defineProperty(process.env, 'KEY', {...}).
• Queries in the form of Object.hasOwn(process.env, 'KEY'), process.env.hasOwnProperty('KEY') or 'KEY' in process.env.
• Deletions in the form of delete process.env.KEY.
• Enumerations inf the form of ...process.env or Object.keys(process.env).

Only the names of the environment variables being accessed are printed. The values are not printed.

--trace-env-js-stack#

--trace-env-native-stack#

--trace-event-categories#

--trace-event-file-pattern#

--trace-events-enabled#

--trace-exit#

--trace-require-module=mode#

Prints information about usage of Loading ECMAScript modules using require().

--trace-sigint#

--trace-sync-io#

--trace-tls#

--trace-uncaught#

Print stack traces for uncaught exceptions; usually, the stack trace associated with the creation of an Error is printed, whereas this makes Node.js also print the stack trace associated with throwing the value (which does not need to be an Error instance).

--trace-warnings#

--track-heap-objects#

--unhandled-rejections=mode#

Changed default mode to throw. Previously, a warning was emitted.

Using this flag allows to change what should happen when an unhandled rejection occurs. One of the following modes can be chosen:

• throw: Emit unhandledRejection. If this hook is not set, raise the unhandled rejection as an uncaught exception. This is the default.
• strict: Raise the unhandled rejection as an uncaught exception. If the exception is handled, unhandledRejection is emitted.
• warn: Always trigger a warning, no matter if the unhandledRejection hook is set or not but do not print the deprecation warning.
• warn-with-error-code: Emit unhandledRejection. If this hook is not set, trigger a warning, and set the process exit code to 1.
• none: Silence all warnings.

--use-bundled-ca, --use-openssl-ca#

Use bundled Mozilla CA store as supplied by current Node.js version or use OpenSSL's default CA store. The default store is selectable at build-time.

The bundled CA store, as supplied by Node.js, is a snapshot of Mozilla CA store that is fixed at release time. It is identical on all supported platforms.

Using OpenSSL store allows for external modifications of the store. For most Linux and BSD distributions, this store is maintained by the distribution maintainers and system administrators. OpenSSL CA store location is dependent on configuration of the OpenSSL library but this can be altered at runtime using environment variables.

--use-env-proxy#

When enabled, Node.js parses the HTTP_PROXY, HTTPS_PROXY and NO_PROXY environment variables during startup, and tunnels requests over the specified proxy.

--use-largepages=mode#

Re-map the Node.js static code to large memory pages at startup. If supported on the target system, this will cause the Node.js static code to be moved onto 2 MiB pages instead of 4 KiB pages.

• off: No mapping will be attempted. This is the default.
• on: If supported by the OS, mapping will be attempted. Failure to map will be ignored and a message will be printed to standard error.
• silent: If supported by the OS, mapping will be attempted. Failure to map will be ignored and will not be reported.

--use-system-ca#

Added support on non-Windows and non-macOS.

Node.js uses the trusted CA certificates present in the system store along with the --use-bundled-ca option and the NODE_EXTRA_CA_CERTS environment variable. On platforms other than Windows and macOS, this loads certificates from the directory and file trusted by OpenSSL, similar to --use-openssl-ca, with the difference being that it caches the certificates after first load.

On Windows and macOS, the certificate trust policy is similar to Chromium's policy for locally trusted certificates, but with some differences:

On macOS, the following settings are respected:

• Default and System Keychains
  • Trust:
    • Any certificate where the “When using this certificate” flag is set to “Always Trust” or
    • Any certificate where the “Secure Sockets Layer (SSL)” flag is set to “Always Trust”.
  • The certificate must also be valid, with "X.509 Basic Policy" set to “Always Trust”.

On Windows, the following settings are respected:

• Local Machine (accessed via certlm.msc)
  • Trust:
    • Trusted Root Certification Authorities
    • Trusted People
    • Enterprise Trust -> Enterprise -> Trusted Root Certification Authorities
    • Enterprise Trust -> Enterprise -> Trusted People
    • Enterprise Trust -> Group Policy -> Trusted Root Certification Authorities
    • Enterprise Trust -> Group Policy -> Trusted People
• Current User (accessed via certmgr.msc)
  • Trust:
    • Trusted Root Certification Authorities
    • Enterprise Trust -> Group Policy -> Trusted Root Certification Authorities

On Windows and macOS, Node.js would check that the user settings for the trusted certificates do not forbid them for TLS server authentication before using them.

Node.js currently does not support distrust/revocation of certificates from another source based on system settings.

--v8-options#

--v8-pool-size=num#

Set V8's thread pool size which will be used to allocate background jobs.

If set to 0 then Node.js will choose an appropriate size of the thread pool based on an estimate of the amount of parallelism.

-v, --version#

--watch#

Test runner now supports running in watch mode.

Starts Node.js in watch mode. When in watch mode, changes in the watched files cause the Node.js process to restart. By default, watch mode will watch the entry point and any required or imported module. Use --watch-path to specify what paths to watch.

This flag cannot be combined with --check, --eval, --interactive, or the REPL.

node --watch index.js
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--watch-kill-signal#

node --watch --watch-kill-signal SIGINT test.js
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--watch-path#

Watch mode is now stable.

Starts Node.js in watch mode and specifies what paths to watch. When in watch mode, changes in the watched paths cause the Node.js process to restart. This will turn off watching of required or imported modules, even when used in combination with --watch.

This flag cannot be combined with --check, --eval, --interactive, --test, or the REPL.

Note: Using --watch-path implicitly enables --watch, which requires a file path and is incompatible with --run, as --run takes precedence and ignores watch mode.

node --watch-path=./src --watch-path=./tests index.js
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--watch-preserve-output#

node --watch --watch-preserve-output test.js
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--zero-fill-buffers#

FORCE_COLOR=[1, 2, 3]#

The FORCE_COLOR environment variable is used to enable ANSI colorized output. The value may be:

• 1, true, or the empty string '' indicate 16-color support,
• 2 to indicate 256-color support, or
• 3 to indicate 16 million-color support.

When FORCE_COLOR is used and set to a supported value, both the NO_COLOR, and NODE_DISABLE_COLORS environment variables are ignored.

NODE_COMPILE_CACHE=dir#

This feature is no longer experimental.

NODE_COMPILE_CACHE_PORTABLE=1#

NODE_DEBUG=module[,…]#

NODE_DEBUG_NATIVE=module[,…]#

NODE_DISABLE_COLORS=1#

NODE_DISABLE_COMPILE_CACHE=1#

NODE_EXTRA_CA_CERTS=file#

When set, the well known "root" CAs (like VeriSign) will be extended with the extra certificates in file. The file should consist of one or more trusted certificates in PEM format. A message will be emitted (once) with process.emitWarning() if the file is missing or malformed, but any errors are otherwise ignored.

Neither the well known nor extra certificates are used when the ca options property is explicitly specified for a TLS or HTTPS client or server.

This environment variable is ignored when node runs as setuid root or has Linux file capabilities set.

NODE_ICU_DATA=file#

NODE_NO_WARNINGS=1#

NODE_OPTIONS=options...#

A space-separated list of command-line options. options... are interpreted before command-line options, so command-line options will override or compound after anything in options.... Node.js will exit with an error if an option that is not allowed in the environment is used, such as -p or a script file.

If an option value contains a space, it can be escaped using double quotes:

NODE_OPTIONS='--require "./my path/file.js"'
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A singleton flag passed as a command-line option will override the same flag passed into NODE_OPTIONS:

# The inspector will be available on port 5555
NODE_OPTIONS='--inspect=localhost:4444' node --inspect=localhost:5555
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A flag that can be passed multiple times will be treated as if its NODE_OPTIONS instances were passed first, and then its command-line instances afterwards:

NODE_OPTIONS='--require "./a.js"' node --require "./b.js"
# is equivalent to:
node --require "./a.js" --require "./b.js"
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Node.js options that are allowed are in the following list. If an option supports both --XX and --no-XX variants, they are both supported but only one is included in the list below.

• --allow-addons
• --allow-child-process
• --allow-ffi
• --allow-fs-read
• --allow-fs-write
• --allow-inspector
• --allow-net
• --allow-wasi
• --allow-worker
• --conditions, -C
• --cpu-prof-dir
• --cpu-prof-interval
• --cpu-prof-name
• --cpu-prof
• --diagnostic-dir
• --disable-proto
• --disable-sigusr1
• --disable-warning
• --disable-wasm-trap-handler
• --dns-result-order
• --enable-fips
• --enable-network-family-autoselection
• --enable-source-maps
• --entry-url
• --experimental-abortcontroller
• --experimental-addon-modules
• --experimental-detect-module
• --experimental-eventsource
• --experimental-ffi
• --experimental-import-meta-resolve
• --experimental-json-modules
• --experimental-loader
• --experimental-modules
• --experimental-print-required-tla
• --experimental-quic
• --experimental-require-module
• --experimental-shadow-realm
• --experimental-specifier-resolution
• --experimental-stream-iter
• --experimental-test-isolation
• --experimental-top-level-await
• --experimental-vm-modules
• --experimental-wasi-unstable-preview1
• --force-context-aware
• --force-fips
• --force-node-api-uncaught-exceptions-policy
• --frozen-intrinsics
• --heap-prof-dir
• --heap-prof-interval
• --heap-prof-name
• --heap-prof
• --heapsnapshot-near-heap-limit
• --heapsnapshot-signal
• --http-parser
• --icu-data-dir
• --import
• --input-type
• --insecure-http-parser
• --inspect-brk
• --inspect-port, --debug-port
• --inspect-publish-uid
• --inspect-wait
• --inspect
• --localstorage-file
• --max-http-header-size
• --max-old-space-size-percentage
• --napi-modules
• --network-family-autoselection-attempt-timeout
• --no-addons
• --no-async-context-frame
• --no-deprecation
• --no-experimental-global-navigator
• --no-experimental-repl-await
• --no-experimental-sqlite
• --no-experimental-strip-types
• --no-experimental-websocket
• --no-experimental-webstorage
• --no-extra-info-on-fatal-exception
• --no-force-async-hooks-checks
• --no-global-search-paths
• --no-network-family-autoselection
• --no-strip-types
• --no-warnings
• --no-webstorage
• --node-memory-debug
• --openssl-config
• --openssl-legacy-provider
• --openssl-shared-config
• --pending-deprecation
• --permission-audit
• --permission
• --preserve-symlinks-main
• --preserve-symlinks
• --prof-process
• --redirect-warnings
• --report-compact
• --report-dir, --report-directory
• --report-exclude-env
• --report-exclude-network
• --report-filename
• --report-on-fatalerror
• --report-on-signal
• --report-signal
• --report-uncaught-exception
• --require-module
• --require, -r
• --secure-heap-min
• --secure-heap
• --snapshot-blob
• --test-coverage-branches
• --test-coverage-exclude
• --test-coverage-functions
• --test-coverage-include
• --test-coverage-lines
• --test-global-setup
• --test-isolation
• --test-name-pattern
• --test-only
• --test-random-seed
• --test-randomize
• --test-reporter-destination
• --test-reporter
• --test-rerun-failures
• --test-shard
• --test-skip-pattern
• --throw-deprecation
• --title
• --tls-cipher-list
• --tls-keylog
• --tls-max-v1.2
• --tls-max-v1.3
• --tls-min-v1.0
• --tls-min-v1.1
• --tls-min-v1.2
• --tls-min-v1.3
• --trace-deprecation
• --trace-env-js-stack
• --trace-env-native-stack
• --trace-env
• --trace-event-categories
• --trace-event-file-pattern
• --trace-events-enabled
• --trace-exit
• --trace-require-module
• --trace-sigint
• --trace-sync-io
• --trace-tls
• --trace-uncaught
• --trace-warnings
• --track-heap-objects
• --unhandled-rejections
• --use-bundled-ca
• --use-env-proxy
• --use-largepages
• --use-openssl-ca
• --use-system-ca
• --v8-pool-size
• --watch-kill-signal
• --watch-path
• --watch-preserve-output
• --watch
• --zero-fill-buffers

V8 options that are allowed are:

• --abort-on-uncaught-exception
• --disallow-code-generation-from-strings
• --enable-etw-stack-walking
• --expose-gc
• --interpreted-frames-native-stack
• --jitless
• --max-heap-size
• --max-old-space-size
• --max-semi-space-size
• --perf-basic-prof-only-functions
• --perf-basic-prof
• --perf-prof-unwinding-info
• --perf-prof
• --stack-trace-limit

--perf-basic-prof-only-functions, --perf-basic-prof, --perf-prof-unwinding-info, and --perf-prof are only available on Linux.

NODE_PATH=path[:…]#

':'-separated list of directories prefixed to the module search path.

NODE_PENDING_DEPRECATION=1#

When set to 1, emit pending deprecation warnings.

NODE_PENDING_PIPE_INSTANCES=instances#

NODE_PRESERVE_SYMLINKS=1#

NODE_REDIRECT_WARNINGS=file#

NODE_REPL_EXTERNAL_MODULE=file#

Remove the possibility to use this env var with kDisableNodeOptionsEnv for embedders.

NODE_REPL_HISTORY=file#

NODE_SKIP_PLATFORM_CHECK=value#

NODE_TEST_CONTEXT=value#

NODE_TLS_REJECT_UNAUTHORIZED=value#

NODE_USE_ENV_PROXY=1#

When enabled, Node.js parses the HTTP_PROXY, HTTPS_PROXY and NO_PROXY environment variables during startup, and tunnels requests over the specified proxy.

NODE_USE_SYSTEM_CA=1#

Node.js uses the trusted CA certificates present in the system store along with the --use-bundled-ca option and the NODE_EXTRA_CA_CERTS environment variable.

NODE_V8_COVERAGE=dir#

When set, Node.js will begin outputting V8 JavaScript code coverage and Source Map data to the directory provided as an argument (coverage information is written as JSON to files with a coverage prefix).

Coverage output#

{
  "result": [
    {
      "scriptId": "67",
      "url": "internal/tty.js",
      "functions": []
    }
  ]
}
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Source map cache#

If found, source map data is appended to the top-level key source-map-cache on the JSON coverage object.

{
  "result": [
    {
      "scriptId": "68",
      "url": "file:///absolute/path/to/source.js",
      "functions": []
    }
  ],
  "source-map-cache": {
    "file:///absolute/path/to/source.js": {
      "url": "./path-to-map.json",
      "data": {
        "version": 3,
        "sources": [
          "file:///absolute/path/to/original.js"
        ],
        "names": [
          "Foo",
          "console",
          "info"
        ],
        "mappings": "MAAMA,IACJC,YAAaC",
        "sourceRoot": "./"
      },
      "lineLengths": [
        13,
        62,
        38,
        27
      ]
    }
  }
}
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NO_COLOR=<any>#

OPENSSL_CONF=file#

Load an OpenSSL configuration file on startup. Among other uses, this can be used to enable FIPS-compliant crypto if Node.js is built with ./configure --openssl-fips.

SSL_CERT_DIR=dir#

If --use-openssl-ca is enabled, or if --use-system-ca is enabled on platforms other than macOS and Windows, this overrides and sets OpenSSL's directory containing trusted certificates.

SSL_CERT_FILE=file#

If --use-openssl-ca is enabled, or if --use-system-ca is enabled on platforms other than macOS and Windows, this overrides and sets OpenSSL's file containing trusted certificates.

TZ#

Changing the TZ variable using process.env.TZ = changes the timezone on POSIX systems.

The TZ environment variable is used to specify the timezone configuration.

$ TZ=Europe/Dublin node -pe "new Date().toString()"
Wed May 12 2021 20:30:48 GMT+0100 (Irish Standard Time)
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UV_THREADPOOL_SIZE=size#

Set the number of threads used in libuv's threadpool to size threads.

Asynchronous system APIs are used by Node.js whenever possible, but where they do not exist, libuv's threadpool is used to create asynchronous node APIs based on synchronous system APIs. Node.js APIs that use the threadpool are:

• all fs APIs, other than the file watcher APIs and those that are explicitly synchronous
• asynchronous crypto APIs such as crypto.pbkdf2(), crypto.scrypt(), crypto.randomBytes(), crypto.randomFill(), crypto.generateKeyPair()
• dns.lookup()
• all zlib APIs, other than those that are explicitly synchronous

Useful V8 options#

--max-heap-size#

Specifies the maximum heap size (in megabytes) for the process.

This option is typically used to limit the amount of memory the process can use for its JavaScript heap.

--max-old-space-size=SIZE (in MiB)#

Sets the max memory size of V8's old memory section. As memory consumption approaches the limit, V8 will spend more time on garbage collection in an effort to free unused memory.

On a machine with 2 GiB of memory, consider setting this to 1536 (1.5 GiB) to leave some memory for other uses and avoid swapping.

node --max-old-space-size=1536 index.js
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--max-semi-space-size=SIZE (in MiB)#

Sets the maximum semi-space size for V8's scavenge garbage collector in MiB (mebibytes). Increasing the max size of a semi-space may improve throughput for Node.js at the cost of more memory consumption.

Since the young generation size of the V8 heap is three times (see YoungGenerationSizeFromSemiSpaceSize in V8) the size of the semi-space, an increase of 1 MiB to semi-space applies to each of the three individual semi-spaces and causes the heap size to increase by 3 MiB. The throughput improvement depends on your workload (see #42511).

The default value depends on the memory limit. For example, on 64-bit systems with a memory limit of 512 MiB, the max size of a semi-space defaults to 1 MiB. For memory limits up to and including 2GiB, the default max size of a semi-space will be less than 16 MiB on 64-bit systems.

To get the best configuration for your application, you should try different max-semi-space-size values when running benchmarks for your application.

for MiB in 16 32 64 128; do
    node --max-semi-space-size=$MiB index.js
done
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--stack-trace-limit=limit#

The maximum number of stack frames to collect in an error's stack trace. Setting it to 0 disables stack trace collection. The default value is 10.

node --stack-trace-limit=12 -p -e "Error.stackTraceLimit" # prints 12
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