Node.js

- About this documentation
- Usage and example

- Assertion testing
- Async hooks
- Buffer
- C++ addons
- C/C++ addons with N-API
- C++ embedder API
- Child processes
- Cluster
- Command line options
- Console
- Crypto
- Debugger
- Deprecated APIs
- DNS
- Domain
- ECMAScript modules
- Errors
- Events
- File system
- Globals
- HTTP
- HTTP/2
- HTTPS
- Inspector
- Internationalization
- Modules
- Net
- OS
- Path
- Performance hooks
- Policies
- Process
- Punycode
- Query strings
- Readline
- REPL
- Report
- Stream
- String decoder
- Timers
- TLS/SSL
- Trace events
- TTY
- UDP/datagram
- URL
- Utilities
- V8
- VM
- WASI
- Worker threads
- Zlib

- Code repository and issue tracker

# Command line options#

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.

To view this documentation as a manual page in a terminal, run `man node`.

## Synopsis#

`node [options] [V8 options] [script.js | -e "script" | -] [--] [arguments]`

`node inspect [script.js | -e "script" | <host>:<port>] …`

`node --v8-options`

Execute without arguments to start the REPL.

For more info about `node inspect`, please see the debugger documentation.

## Options#

History

Version | Changes
--- | ---
v10.12.0 | 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`.

### `-`#

Added in: v8.0.0

Alias for stdin. Analogous to the use of `-` in other command line utilities, meaning that the script will be read from stdin, and the rest of the options are passed to that script.

### `--`#

Added in: v6.11.0

Indicate the end of node options. Pass the rest of the arguments to the script. If no script filename or eval/print script is supplied prior to this, then the next argument will be used as a script filename.

### `--abort-on-uncaught-exception`#

Added in: v0.10.8

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

If this flag is passed, the behavior can still be set to not abort through `process.setUncaughtExceptionCaptureCallback()` (and through usage of the `domain` module that uses it).

### `--completion-bash`#

Added in: v10.12.0

Print source-able bash completion script for Node.js.

    $ node --completion-bash > node_bash_completion
    $ source node_bash_completion

### `--cpu-prof`#

Added in: v12.0.0

Stability: 1 - Experimental

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 will be placed in the current working directory.

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

    $ node --cpu-prof index.js
    $ ls *.cpuprofile
    CPU.20190409.202950.15293.0.0.cpuprofile

### `--cpu-prof-dir`#

Added in: v12.0.0

Stability: 1 - Experimental

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

The default value is controlled by the --diagnostic-dir command line option.

### `--cpu-prof-interval`#

Added in: v12.2.0

Stability: 1 - Experimental

Specify the sampling interval in microseconds for the CPU profiles generated by `--cpu-prof`. The default is 1000 microseconds.

### `--cpu-prof-name`#

Added in: v12.0.0

Stability: 1 - Experimental

Specify the file name of the CPU profile generated by `--cpu-prof`.

### `--diagnostic-dir=directory`#

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

Affects the default output directory of:

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

### `--disable-proto=mode`#

Disable the `Object.prototype.__proto__` property. If `mode` is `delete`, the property will be removed entirely. If `mode` is `throw`, accesses to the property will throw an exception with the code `ERR_PROTO_ACCESS`.

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

Added in: v9.8.0

Make built-in language features like `eval` and `new Function` that generate code from strings throw an exception instead. This does not affect the Node.js `vm` module.

### `--enable-fips`#

Added in: v6.0.0

Enable FIPS-compliant crypto at startup. (Requires Node.js to be built with `./configure --openssl-fips`.)

### `--enable-source-maps`#

Added in: v12.12.0

Stability: 1 - Experimental

Enable experimental Source Map v3 support for stack traces.

Currently, overriding `Error.prepareStackTrace` is ignored when the `--enable-source-maps` flag is set.

### `--experimental-import-meta-resolve`#

Added in: v13.9.0, v12.16.2

Enable experimental `import.meta.resolve()` support.

### `--experimental-json-modules`#

Added in: v12.9.0

Enable experimental JSON support for the ES Module loader.

### `--experimental-loader=module`#

Added in: v9.0.0

Specify the `module` of a custom experimental ECMAScript Module loader. `module` may be either a path to a file, or an ECMAScript Module name.

### `--experimental-modules`#

Added in: v8.5.0

Enable latest experimental modules features (deprecated).

### `--experimental-policy`#

Added in: v11.8.0

Use the specified file as a security policy.

### `--experimental-repl-await`#

Added in: v10.0.0

Enable experimental top-level `await` keyword support in REPL.

### `--experimental-specifier-resolution=mode`#

Added in: v13.4.0, v12.16.0

Sets the resolution algorithm for resolving ES module specifiers. Valid options are `explicit` and `node`.

The default is `explicit`, which requires providing the full path to a module. The `node` mode will enable support for optional file extensions and the ability to import a directory that has an index file.

Please see customizing ESM specifier resolution for example usage.

### `--experimental-top-level-await`#

Added in: v14.3.0

Enable experimental top-level `await` keyword support, available only in ES module scripts.

(See also `--experimental-repl-await`.)

### `--experimental-vm-modules`#

Added in: v9.6.0

Enable experimental ES Module support in the `vm` module.

### `--experimental-wasi-unstable-preview1`#

History

Version | Changes
--- | ---
v13.6.0 | changed from `--experimental-wasi-unstable-preview0` to `--experimental-wasi-unstable-preview1`
v13.3.0, v12.16.0 | Added in: v13.3.0, v12.16.0

Enable experimental WebAssembly System Interface (WASI) support.

### `--experimental-wasm-modules`#

Added in: v12.3.0

### `--force-context-aware`#

Added in: v12.12.0

Disable loading native addons that are not context-aware.

Enable experimental WebAssembly module support.

### `--force-fips`#

Added in: v6.0.0

Force FIPS-compliant crypto on startup. (Cannot be disabled from script code.) (Same requirements as `--enable-fips`.)

### `--frozen-intrinsics`#

Added in: v11.12.0

Stability: 1 - Experimental

Enable experimental frozen intrinsics like `Array` and `Object`.

Support is currently only provided for the root context and no guarantees are currently provided that `global.Array` is indeed the default intrinsic reference. Code may break under this flag.

`--require` runs prior to freezing intrinsics in order to allow polyfills to be added.

### `--heapsnapshot-signal=signal`#

Added in: v12.0.0

Enables a signal handler that causes the Node.js process to write a heap dump when the specified signal is received. `signal` must be a valid signal name. Disabled by default.

    $ 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

### `--heap-prof`#

Added in: v12.4.0

Stability: 1 - Experimental

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 will be placed in the current working directory.

If `--heap-prof-name` is not specified, the generated profile will be named `Heap.${yyyymmdd}.${hhmmss}.${pid}.${tid}.${seq}.heapprofile`.

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

### `--heap-prof-dir`#

Added in: v12.4.0

Stability: 1 - Experimental

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

The default value is controlled by the --diagnostic-dir command line option.

### `--heap-prof-interval`#

Added in: v12.4.0

Stability: 1 - Experimental

Specify the average sampling interval in bytes for the heap profiles generated by `--heap-prof`. The default is 512 * 1024 bytes.

### `--heap-prof-name`#

Added in: v12.4.0

Stability: 1 - Experimental

Specify the file name of the heap profile generated by `--heap-prof`.

### `--icu-data-dir=file`#

Added in: v0.11.15

Specify ICU data load path. (Overrides `NODE_ICU_DATA`.)

### `--input-type=type`#

Added in: v12.0.0

This configures Node.js to interpret string input as CommonJS or as an ES module. String input is input via `--eval`, `--print`, or `STDIN`.

Valid values are `"commonjs"` and `"module"`. The default is `"commonjs"`.

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

Added in: v7.6.0

Activate inspector on `host:port` and break at start of user script. Default `host:port` is `127.0.0.1:9229`.

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

Added in: v7.6.0

Set the `host:port` to be used when the inspector is activated. Useful when activating the inspector by sending the `SIGUSR1` signal.

Default host is `127.0.0.1`.

See the security warning below regarding the `host` parameter usage.

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

Added in: v6.3.0

Activate inspector on `host:port`. Default is `127.0.0.1:9229`.

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.

#### 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.

See the debugging security implications section for more information.

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

Specify ways of the inspector web socket url exposure.

By default inspector websocket url is available in stderr and under `/json/list` endpoint on `http://host:port/json/list`.

### `--insecure-http-parser`#

Added in: v13.4.0, v12.15.0, v10.19.0

Use an insecure HTTP parser that accepts invalid HTTP headers. This may allow interoperability with non-conformant HTTP implementations. It may also allow request smuggling and other HTTP attacks that rely on invalid headers being accepted. Avoid using this option.

### `--jitless`#

Added in: v12.0.0

Disable runtime allocation of executable memory. This may be required on some platforms for security reasons. It can also reduce attack surface on other platforms, but the performance impact may be severe.

This flag is inherited from V8 and is subject to change upstream. It may disappear in a non-semver-major release.

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

History

Version | Changes
--- | ---
v14.0.0 | Change maximum default size of HTTP headers from 8KB to 16KB.
v11.6.0, v10.15.0 | Added in: v11.6.0, v10.15.0

Specify the maximum size, in bytes, of HTTP headers. Defaults to 16KB.

### `--napi-modules`#

Added in: v7.10.0

This option is a no-op. It is kept for compatibility.

### `--no-deprecation`#

Added in: v0.8.0

Silence deprecation warnings.

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

Added in: v9.0.0

Disables runtime checks for `async_hooks`. These will still be enabled dynamically when `async_hooks` is enabled.

### `--no-warnings`#

Added in: v6.0.0

Silence all process warnings (including deprecations).

### `--openssl-config=file`#

Added in: v6.9.0

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`.

### `--pending-deprecation`#

Added in: v8.0.0

Emit pending deprecation warnings.

Pending deprecations are generally identical to a runtime deprecation with the notable exception that they are turned off by default and will not be emitted unless either the `--pending-deprecation` command line flag, or the `NODE_PENDING_DEPRECATION=1` environment variable, is set. Pending deprecations are used to provide a kind of selective "early warning" mechanism that developers may leverage to detect deprecated API usage.

### `--policy-integrity=sri`#

Added in: v12.7.0

Stability: 1 - Experimental

Instructs Node.js to error prior to running any code if the policy does not have the specified integrity. It expects a Subresource Integrity string as a parameter.

### `--preserve-symlinks`#

Added in: v6.3.0

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

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).

The `--preserve-symlinks` flag does not apply to the main module, which allows `node --preserve-symlinks node_module/.bin/<foo>` to work. To apply the same behavior for the main module, also use `--preserve-symlinks-main`.

### `--preserve-symlinks-main`#

Added in: v10.2.0

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`; it is expected that `--preserve-symlinks-main` will be used in addition to `--preserve-symlinks` when it is not desirable to follow symlinks before resolving relative paths.

See `--preserve-symlinks` for more information.

### `--prof`#

Added in: v2.0.0

Generate V8 profiler output.

### `--prof-process`#

Added in: v5.2.0

Process V8 profiler output generated using the V8 option `--prof`.

### `--redirect-warnings=file`#

Added in: v8.0.0

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.

The `file` name may be an absolute path. If it is not, the default directory it will be written to is controlled by the --diagnostic-dir command line option.

### `--report-compact`#

Added in: v13.12.0

Write reports in a compact format, single-line JSON, more easily consumable by log processing systems than the default multi-line format designed for human consumption.

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

History

Version | Changes
--- | ---
v13.12.0 | This option is no longer experimental.
v12.0.0 | Changed from `--diagnostic-report-directory` to `--report-directory`
v11.8.0 | Added in: v11.8.0

Location at which the report will be generated.

### `--report-filename=filename`#

History

Version | Changes
--- | ---
v13.12.0 | This option is no longer experimental.
v12.0.0 | changed from `--diagnostic-report-filename` to `--report-filename`
v11.8.0 | Added in: v11.8.0

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

### `--report-on-fatalerror`#

History

Version | Changes
--- | ---
v14.0.0 | This option is no longer experimental.
v12.0.0 | changed from `--diagnostic-report-on-fatalerror` to `--report-on-fatalerror`
v11.8.0 | Added in: v11.8.0

Enables the report to be triggered on fatal errors (internal errors within the Node.js runtime such as out of memory) that lead to termination of the application. Useful to inspect various diagnostic data elements such as heap, stack, event loop state, resource consumption etc. to reason about the fatal error.

### `--report-on-signal`#

History

Version | Changes
--- | ---
v13.12.0 | This option is no longer experimental.
v12.0.0 | changed from `--diagnostic-report-on-signal` to `--report-on-signal`
v11.8.0 | Added in: v11.8.0

Enables report to be generated upon receiving the specified (or predefined) signal to the running Node.js process. The signal to trigger the report is specified through `--report-signal`.

### `--report-signal=signal`#

History

Version | Changes
--- | ---
v13.12.0 | This option is no longer experimental.
v12.0.0 | changed from `--diagnostic-report-signal` to `--report-signal`
v11.8.0 | Added in: v11.8.0

Sets or resets the signal for report generation (not supported on Windows). Default signal is `SIGUSR2`.

### `--report-uncaught-exception`#

History

Version | Changes
--- | ---
v13.12.0 | This option is no longer experimental.
v12.0.0 | changed from `--diagnostic-report-uncaught-exception` to `--report-uncaught-exception`
v11.8.0 | Added in: v11.8.0

Enables report to be generated on uncaught exceptions. Useful when inspecting the JavaScript stack in conjunction with native stack and other runtime environment data.

### `--throw-deprecation`#

Added in: v0.11.14

Throw errors for deprecations.

### `--title=title`#

Added in: v10.7.0

Set `process.title` on startup.

### `--tls-cipher-list=list`#

Added in: v4.0.0

Specify an alternative default TLS cipher list. Requires Node.js to be built with crypto support (default).

### `--tls-keylog=file`#

Added in: v13.2.0, v12.16.0

Log TLS key material to a file. The key material is in NSS `SSLKEYLOGFILE` format and can be used by software (such as Wireshark) to decrypt the TLS traffic.

### `--tls-max-v1.2`#

Added in: v12.0.0, v10.20.0

Set `tls.DEFAULT_MAX_VERSION` to 'TLSv1.2'. Use to disable support for TLSv1.3.

### `--tls-max-v1.3`#

Added in: v12.0.0

Set default `tls.DEFAULT_MAX_VERSION` to 'TLSv1.3'. Use to enable support for TLSv1.3.

### `--tls-min-v1.0`#

Added in: v12.0.0, v10.20.0

Set default `tls.DEFAULT_MIN_VERSION` to 'TLSv1'. Use for compatibility with old TLS clients or servers.

### `--tls-min-v1.1`#

Added in: v12.0.0, v10.20.0

Set default `tls.DEFAULT_MIN_VERSION` to 'TLSv1.1'. Use for compatibility with old TLS clients or servers.

### `--tls-min-v1.2`#

Added in: v12.2.0, v10.20.0

Set default `tls.DEFAULT_MIN_VERSION` to 'TLSv1.2'. This is the default for 12.x and later, but the option is supported for compatibility with older Node.js versions.

### `--tls-min-v1.3`#

Added in: v12.0.0

Set default `tls.DEFAULT_MIN_VERSION` to 'TLSv1.3'. Use to disable support for TLSv1.2, which is not as secure as TLSv1.3.

### `--trace-atomics-wait`#

Added in: v14.3.0

Print short summaries of calls to `Atomics.wait()` to stderr. The output could look like this:

    (node:15701) [Thread 0] Atomics.wait(