# Deprecated APIs

Node.js may deprecate APIs when either: (a) use of the API is considered to be
unsafe, (b) an improved alternative API has been made available, or (c)
breaking changes to the API are expected in a future major release.

Node.js utilizes three kinds of Deprecations:

* Documentation-only
* Runtime
* End-of-Life

A Documentation-only deprecation is one that is expressed only within the
Node.js API docs. These generate no side-effects while running Node.js.

A Runtime deprecation will, by default, generate a process warning that will
be printed to `stderr` the first time the deprecated API is used. When the
`--throw-deprecation` command-line flag is used, a Runtime deprecation will
cause an error to be thrown.

An End-of-Life deprecation is used to identify code that either has been
removed or will soon be removed from Node.js.

## Un-deprecation

From time-to-time the deprecation of an API may be reversed. Such action may
happen in either a semver-minor or semver-major release. In such situations,
this document will be updated with information relevant to the decision.
*However, the deprecation identifier will not be modified*.

## List of Deprecated APIs

<a id="DEP0001"></a>
### DEP0001: http.OutgoingMessage.prototype.flush

Type: Runtime

The `OutgoingMessage.prototype.flush()` method is deprecated. Use
`OutgoingMessage.prototype.flushHeaders()` instead.

<a id="DEP0002"></a>
### DEP0002: require('\_linklist')

Type: Runtime

The `_linklist` module is deprecated. Please use a userland alternative.

<a id="DEP0003"></a>
### DEP0003: \_writableState.buffer

Type: Runtime

The `_writableState.buffer` property is deprecated. Use the
`_writableState.getBuffer()` method instead.

<a id="DEP0004"></a>
### DEP0004: CryptoStream.prototype.readyState

Type: Documentation-only

The `CryptoStream.prototype.readyState` property is deprecated and should not
be used.

<a id="DEP0005"></a>
### DEP0005: Buffer() constructor

Type: Documentation-only

The `Buffer()` function and `new Buffer()` constructor are deprecated due to
API usability issues that can potentially lead to accidental security issues.

As an alternative, use of the following methods of constructing `Buffer` objects
is strongly recommended:

* [`Buffer.alloc(size[, fill[, encoding]])`][alloc] - Create a `Buffer` with
  *initialized* memory.
* [`Buffer.allocUnsafe(size)`][alloc_unsafe_size] - Create a `Buffer` with *uninitialized*
  memory.
* [`Buffer.allocUnsafeSlow(size)`][] - Create a `Buffer` with *uninitialized*
   memory.
* [`Buffer.from(array)`][] - Create a `Buffer` with a copy of `array`
* [`Buffer.from(arrayBuffer[, byteOffset[, length]])`][from_arraybuffer] - Create a `Buffer`
  that wraps the given `arrayBuffer`.
* [`Buffer.from(buffer)`][] - Create a `Buffer` that copies `buffer`.
* [`Buffer.from(string[, encoding])`][from_string_encoding] - Create a `Buffer` that copies
  `string`.

<a id="DEP0006"></a>
### DEP0006: child\_process options.customFds

Type: Runtime

Within the [`child_process`][] module's `spawn()`, `fork()`, and `exec()`
methods, the `options.customFds` option is deprecated. The `options.stdio`
option should be used instead.

<a id="DEP0007"></a>
### DEP0007: cluster worker.suicide

Type: Runtime

Within the `cluster` module, the [`worker.suicide`][] property has been
deprecated. Please use [`worker.exitedAfterDisconnect`][] instead.

<a id="DEP0008"></a>
### DEP0008: require('constants')

Type: Documentation-only

The `constants` module has been deprecated. When requiring access to constants
relevant to specific Node.js builtin modules, developers should instead refer
to the `constants` property exposed by the relevant module. For instance,
`require('fs').constants` and `require('os').constants`.

<a id="DEP0009"></a>
### DEP0009: crypto.pbkdf2 without digest

Type: End-of-life

Use of the [`crypto.pbkdf2()`][] API without specifying a digest was deprecated
in Node.js 6.0 because the method defaulted to using the non-recommended
`'SHA1'` digest. Previously, a deprecation warning was printed. Starting in
Node.js 8.0.0, calling `crypto.pbkdf2()` or `crypto.pbkdf2Sync()` with an
undefined `digest` will throw a `TypeError`.

<a id="DEP0010"></a>
### DEP0010: crypto.createCredentials

Type: Runtime

The [`crypto.createCredentials()`][] API is deprecated. Please use
[`tls.createSecureContext()`][] instead.

<a id="DEP0011"></a>
### DEP0011: crypto.Credentials

Type: Runtime

The `crypto.Credentials` class is deprecated. Please use [`tls.SecureContext`][]
instead.

<a id="DEP0012"></a>
### DEP0012: Domain.dispose

Type: Runtime

[`Domain.dispose()`][] is deprecated. Recover from failed I/O actions
explicitly via error event handlers set on the domain instead.

<a id="DEP0013"></a>
### DEP0013: fs asynchronous function without callback

Type: Runtime

Calling an asynchronous function without a callback is deprecated.

<a id="DEP0014"></a>
### DEP0014: fs.read legacy String interface

Type: End-of-Life

The [`fs.read()`][] legacy String interface is deprecated. Use the Buffer API as
mentioned in the documentation instead.

<a id="DEP0015"></a>
### DEP0015: fs.readSync legacy String interface

Type: End-of-Life

The [`fs.readSync()`][] legacy String interface is deprecated. Use the Buffer
API as mentioned in the documentation instead.

<a id="DEP0016"></a>
### DEP0016: GLOBAL/root

Type: Runtime

The `GLOBAL` and `root` aliases for the `global` property have been deprecated
and should no longer be used.

<a id="DEP0017"></a>
### DEP0017: Intl.v8BreakIterator

Type: Runtime

The `Intl.v8BreakIterator` is deprecated and will be removed or replaced soon.

<a id="DEP0018"></a>
### DEP0018: Unhandled promise rejections

Type: Runtime

Unhandled promise rejections are deprecated. In the future, promise rejections
that are not handled will terminate the Node.js process with a non-zero exit
code.

<a id="DEP0019"></a>
### DEP0019: require('.') resolved outside directory

Type: Runtime

In certain cases, `require('.')` may resolve outside the package directory.
This behavior is deprecated and will be removed in a future major Node.js
release.

<a id="DEP0020"></a>
### DEP0020: Server.connections

Type: Runtime

The [`Server.connections`][] property is deprecated. Please use the
[`Server.getConnections()`][] method instead.

<a id="DEP0021"></a>
### DEP0021: Server.listenFD

Type: Runtime

The `Server.listenFD()` method is deprecated. Please use
[`Server.listen({fd: <number>})`][] instead.

<a id="DEP0022"></a>
### DEP0022: os.tmpDir()

Type: Runtime

The `os.tmpDir()` API is deprecated. Please use [`os.tmpdir()`][] instead.

<a id="DEP0023"></a>
### DEP0023: os.getNetworkInterfaces()

Type: Runtime

The `os.getNetworkInterfaces()` method is deprecated. Please use the
[`os.networkInterfaces`][] property instead.

<a id="DEP0024"></a>
### DEP0024: REPLServer.prototype.convertToContext()

Type: Runtime

The `REPLServer.prototype.convertToContext()` API is deprecated and should
not be used.

<a id="DEP0025"></a>
### DEP0025: require('sys')

Type: Runtime

The `sys` module is deprecated. Please use the [`util`][] module instead.

<a id="DEP0026"></a>
### DEP0026: util.print()

Type: Runtime

The [`util.print()`][] API is deprecated. Please use [`console.log()`][]
instead.

<a id="DEP0027"></a>
### DEP0027: util.puts()

Type: Runtime

The [`util.puts()`][] API is deprecated. Please use [`console.log()`][] instead.

<a id="DEP0028"></a>
### DEP0028: util.debug()

Type: Runtime

The [`util.debug()`][] API is deprecated. Please use [`console.error()`][]
instead.

<a id="DEP0029"></a>
### DEP0029: util.error()

Type: Runtime

The [`util.error()`][] API is deprecated. Please use [`console.error()`][]
instead.

<a id="DEP0030"></a>
### DEP0030: SlowBuffer

Type: Documentation-only

The [`SlowBuffer`][] class has been deprecated. Please use
[`Buffer.allocUnsafeSlow(size)`][] instead.

<a id="DEP0031"></a>
### DEP0031: ecdh.setPublicKey()

Type: Documentation-only

The [`ecdh.setPublicKey()`][] method is now deprecated as its inclusion in the
API is not useful.

<a id="DEP0032"></a>
### DEP0032: domain module

Type: Documentation-only

The [`domain`][] module is deprecated and should not be used.

<a id="DEP0033"></a>
### DEP0033: EventEmitter.listenerCount()

Type: Documentation-only

The [`EventEmitter.listenerCount(emitter, eventName)`][] API has been
deprecated. Please use [`emitter.listenerCount(eventName)`][] instead.

<a id="DEP0034"></a>
### DEP0034: fs.exists(path, callback)

Type: Documentation-only

The [`fs.exists(path, callback)`][] API has been deprecated. Please use
[`fs.stat()`][] or [`fs.access()`][] instead.

<a id="DEP0035"></a>
### DEP0035: fs.lchmod(path, mode, callback)

Type: Documentation-only

The [`fs.lchmod(path, mode, callback)`][] API has been deprecated.

<a id="DEP0036"></a>
### DEP0036: fs.lchmodSync(path, mode)

Type: Documentation-only

The [`fs.lchmodSync(path, mode)`][] API has been deprecated.

<a id="DEP0037"></a>
### DEP0037: fs.lchown(path, uid, gid, callback)

Type: Documentation-only

The [`fs.lchown(path, uid, gid, callback)`][] API has been deprecated.

<a id="DEP0038"></a>
### DEP0038: fs.lchownSync(path, uid, gid)

Type: Documentation-only

The [`fs.lchownSync(path, uid, gid)`][] API has been deprecated.

<a id="DEP0039"></a>
### DEP0039: require.extensions

Type: Documentation-only

The [`require.extensions`][] property has been deprecated.

<a id="DEP0040"></a>
### DEP0040: punycode module

Type: Documentation-only

The [`punycode`][] module has been deprecated. Please use a userland alternative
instead.

<a id="DEP0041"></a>
### DEP0041: NODE\_REPL\_HISTORY\_FILE environment variable

Type: Documentation-only

The `NODE_REPL_HISTORY_FILE` environment variable has been deprecated.

<a id="DEP0042"></a>
### DEP0042: tls.CryptoStream

Type: Documentation-only

The [`tls.CryptoStream`][] class has been deprecated. Please use
[`tls.TLSSocket`][] instead.

<a id="DEP0043"></a>
### DEP0043: tls.SecurePair

Type: Documentation-only

The [`tls.SecurePair`][] class has been deprecated. Please use
[`tls.TLSSocket`][] instead.

<a id="DEP0044"></a>
### DEP0044: util.isArray()

Type: Documentation-only

The [`util.isArray()`][] API has been deprecated. Please use `Array.isArray()`
instead.

<a id="DEP0045"></a>
### DEP0045: util.isBoolean()

Type: Documentation-only

The [`util.isBoolean()`][] API has been deprecated.

<a id="DEP0046"></a>
### DEP0046: util.isBuffer()

Type: Documentation-only

The [`util.isBuffer()`][] API has been deprecated. Please use
[`Buffer.isBuffer()`][] instead.

<a id="DEP0047"></a>
### DEP0047: util.isDate()

Type: Documentation-only

The [`util.isDate()`][] API has been deprecated.

<a id="DEP0048"></a>
### DEP0048: util.isError()

Type: Documentation-only

The [`util.isError()`][] API has been deprecated.

<a id="DEP0049"></a>
### DEP0049: util.isFunction()

Type: Documentation-only

The [`util.isFunction()`][] API has been deprecated.

<a id="DEP0050"></a>
### DEP0050: util.isNull()

Type: Documentation-only

The [`util.isNull()`][] API has been deprecated.

<a id="DEP0051"></a>
### DEP0051: util.isNullOrUndefined()

Type: Documentation-only

The [`util.isNullOrUndefined()`][] API has been deprecated.

<a id="DEP0052"></a>
### DEP0052: util.isNumber()

Type: Documentation-only

The [`util.isNumber()`][] API has been deprecated.

<a id="DEP0053"></a>
### DEP0053 util.isObject()

Type: Documentation-only

The [`util.isObject()`][] API has been deprecated.

<a id="DEP0054"></a>
### DEP0054: util.isPrimitive()

Type: Documentation-only

The [`util.isPrimitive()`][] API has been deprecated.

<a id="DEP0055"></a>
### DEP0055: util.isRegExp()

Type: Documentation-only

The [`util.isRegExp()`][] API has been deprecated.

<a id="DEP0056"></a>
### DEP0056: util.isString()

Type: Documentation-only

The [`util.isString()`][] API has been deprecated.

<a id="DEP0057"></a>
### DEP0057: util.isSymbol()

Type: Documentation-only

The [`util.isSymbol()`][] API has been deprecated.

<a id="DEP0058"></a>
### DEP0058: util.isUndefined()

Type: Documentation-only

The [`util.isUndefined()`][] API has been deprecated.

<a id="DEP0059"></a>
### DEP0059: util.log()

Type: Documentation-only

The [`util.log()`][] API has been deprecated.

<a id="DEP0060"></a>
### DEP0060: util.\_extend()

Type: Documentation-only

The [`util._extend()`][] API has been deprecated.

<a id="DEP0061"></a>
### DEP0061: fs.SyncWriteStream

Type: Runtime

The `fs.SyncWriteStream` class was never intended to be a publicly accessible
API. No alternative API is available. Please use a userland alternative.

<a id="DEP0062"></a>
### DEP0062: node --debug

Type: Runtime

`--debug` activates the legacy V8 debugger interface, which has been removed as
of V8 5.8. It is replaced by Inspector which is activated with `--inspect`
instead.

<a id="DEP0063"></a>
### DEP0063: ServerResponse.prototype.writeHeader()

Type: Documentation-only

The `http` module `ServerResponse.prototype.writeHeader()` API has been
deprecated. Please use `ServerResponse.prototype.writeHead()` instead.

*Note*: The `ServerResponse.prototype.writeHeader()` method was never
documented as an officially supported API.

<a id="DEP0064"></a>
### DEP0064: tls.createSecurePair()

Type: Runtime

The `tls.createSecurePair()` API was deprecated in documentation in Node.js
0.11.3. Users should use `tls.Socket` instead.

<a id="DEP0065"></a>
### DEP0065: repl.REPL_MODE_MAGIC and NODE_REPL_MODE=magic

Type: Documentation-only

The `repl` module's `REPL_MODE_MAGIC` constant, used for `replMode` option, has
been deprecated. Its behavior has been functionally identical to that of
`REPL_MODE_SLOPPY` since Node.js v6.0.0, when V8 5.0 was imported. Please use
`REPL_MODE_SLOPPY` instead.

The `NODE_REPL_MODE` environment variable is used to set the underlying
`replMode` of an interactive `node` session. Its default value, `magic`, is
similarly deprecated in favor of `sloppy`.

<a id="DEP0066"></a>
### DEP0066: outgoingMessage.\_headers, outgoingMessage.\_headerNames

Type: Documentation-only

The `http` module `outgoingMessage._headers` and `outgoingMessage._headerNames`
properties have been deprecated. Please instead use one of the public methods
(e.g. `outgoingMessage.getHeader()`, `outgoingMessage.getHeaders()`,
`outgoingMessage.getHeaderNames()`, `outgoingMessage.hasHeader()`,
`outgoingMessage.removeHeader()`, `outgoingMessage.setHeader()`) for working
with outgoing headers.

*Note*: `outgoingMessage._headers` and `outgoingMessage._headerNames` were
never documented as officially supported properties.

<a id="DEP0067"></a>
### DEP0067: OutgoingMessage.prototype.\_renderHeaders

Type: Documentation-only

The `http` module `OutgoingMessage.prototype._renderHeaders()` API has been
deprecated.

*Note*: `OutgoingMessage.prototype._renderHeaders` was never documented as
an officially supported API.

<a id="DEP0068"></a>
### DEP0068: node debug

Type: Runtime

`node debug` corresponds to the legacy CLI debugger which has been replaced with
a V8-inspector based CLI debugger available through `node inspect`.

<a id="DEP0069"></a>
### DEP0069: vm.runInDebugContext(string)

Type: Documentation-only

The DebugContext will be removed in V8 soon and will not be available in Node
10+.

*Note*: DebugContext was an experimental API.

<a id="DEP0070"></a>
### DEP0070: async_hooks.currentId()

Type: Runtime

`async_hooks.currentId()` was renamed to `async_hooks.executionAsyncId()` for
clarity.

*Note*: change was made while `async_hooks` was an experimental API.

<a id="DEP0071"></a>
### DEP0071: async_hooks.triggerId()

Type: Runtime

`async_hooks.triggerId()` was renamed to `async_hooks.triggerAsyncId()` for
clarity.

*Note*: change was made while `async_hooks` was an experimental API.

<a id="DEP0072"></a>
### DEP0072: async_hooks.AsyncResource.triggerId()

Type: Runtime

`async_hooks.AsyncResource.triggerId()` was renamed to
`async_hooks.AsyncResource.triggerAsyncId()` for clarity.

*Note*: change was made while `async_hooks` was an experimental API.

<a id="DEP0076"></a>
### DEP0076: tls.parseCertString()

Type: Documentation-only

`tls.parseCertString()` is a trivial parsing helper that was made public by
mistake. This function can usually be replaced with:

```js
const querystring = require('querystring');
querystring.parse(str, '\n', '=');
```

*Note*: This function is not completely equivalent to `querystring.parse()`. One
difference is that `querystring.parse()` does url decoding:

```sh
> querystring.parse('%E5%A5%BD=1', '\n', '=');
{ '好': '1' }
> tls.parseCertString('%E5%A5%BD=1');
{ '%E5%A5%BD': '1' }
```

<a id="DEP0079"></a>
### DEP0079: Custom inspection function on Objects via .inspect()

Type: Documentation-only

Using a property named `inspect` on an object to specify a custom inspection
function for [`util.inspect()`][] is deprecated. Use [`util.inspect.custom`][]
instead. For backwards compatibility with Node.js prior to version 6.4.0, both
may be specified.

[`Buffer.allocUnsafeSlow(size)`]: buffer.html#buffer_class_method_buffer_allocunsafeslow_size
[`Buffer.from(array)`]: buffer.html#buffer_class_method_buffer_from_array
[`Buffer.from(buffer)`]: buffer.html#buffer_class_method_buffer_from_buffer
[`Buffer.isBuffer()`]: buffer.html#buffer_class_method_buffer_isbuffer_obj
[`Domain.dispose()`]: domain.html#domain_domain_dispose
[`EventEmitter.listenerCount(emitter, eventName)`]: events.html#events_eventemitter_listenercount_emitter_eventname
[`Server.connections`]: net.html#net_server_connections
[`Server.getConnections()`]: net.html#net_server_getconnections_callback
[`Server.listen({fd: <number>})`]: net.html#net_server_listen_handle_backlog_callback
[`SlowBuffer`]: buffer.html#buffer_class_slowbuffer
[`child_process`]: child_process.html
[`console.error()`]: console.html#console_console_error_data_args
[`console.log()`]: console.html#console_console_log_data_args
[`crypto.createCredentials()`]: crypto.html#crypto_crypto_createcredentials_details
[`crypto.pbkdf2()`]: crypto.html#crypto_crypto_pbkdf2_password_salt_iterations_keylen_digest_callback
[`domain`]: domain.html
[`ecdh.setPublicKey()`]: crypto.html#crypto_ecdh_setpublickey_publickey_encoding
[`emitter.listenerCount(eventName)`]: events.html#events_emitter_listenercount_eventname
[`fs.access()`]: fs.html#fs_fs_access_path_mode_callback
[`fs.exists(path, callback)`]: fs.html#fs_fs_exists_path_callback
[`fs.lchmod(path, mode, callback)`]: fs.html#fs_fs_lchmod_path_mode_callback
[`fs.lchmodSync(path, mode)`]: fs.html#fs_fs_lchmodsync_path_mode
[`fs.lchown(path, uid, gid, callback)`]: fs.html#fs_fs_lchown_path_uid_gid_callback
[`fs.lchownSync(path, uid, gid)`]: fs.html#fs_fs_lchownsync_path_uid_gid
[`fs.read()`]: fs.html#fs_fs_read_fd_buffer_offset_length_position_callback
[`fs.readSync()`]: fs.html#fs_fs_readsync_fd_buffer_offset_length_position
[`fs.stat()`]: fs.html#fs_fs_stat_path_callback
[`os.networkInterfaces`]: os.html#os_os_networkinterfaces
[`os.tmpdir()`]: os.html#os_os_tmpdir
[`punycode`]: punycode.html
[`require.extensions`]: modules.html#modules_require_extensions
[`tls.CryptoStream`]: tls.html#tls_class_cryptostream
[`tls.SecureContext`]: tls.html#tls_tls_createsecurecontext_options
[`tls.SecurePair`]: tls.html#tls_class_securepair
[`tls.TLSSocket`]: tls.html#tls_class_tls_tlssocket
[`tls.createSecureContext()`]: tls.html#tls_tls_createsecurecontext_options
[`util._extend()`]: util.html#util_util_extend_target_source
[`util.debug()`]: util.html#util_util_debug_string
[`util.error()`]: util.html#util_util_error_strings
[`util.inspect()`]: util.html#util_util_inspect_object_options
[`util.inspect.custom`]: util.html#util_util_inspect_custom
[`util.isArray()`]: util.html#util_util_isarray_object
[`util.isBoolean()`]: util.html#util_util_isboolean_object
[`util.isBuffer()`]: util.html#util_util_isbuffer_object
[`util.isDate()`]: util.html#util_util_isdate_object
[`util.isError()`]: util.html#util_util_iserror_object
[`util.isFunction()`]: util.html#util_util_isfunction_object
[`util.isNull()`]: util.html#util_util_isnull_object
[`util.isNullOrUndefined()`]: util.html#util_util_isnullorundefined_object
[`util.isNumber()`]: util.html#util_util_isnumber_object
[`util.isObject()`]: util.html#util_util_isobject_object
[`util.isPrimitive()`]: util.html#util_util_isprimitive_object
[`util.isRegExp()`]: util.html#util_util_isregexp_object
[`util.isString()`]: util.html#util_util_isstring_object
[`util.isSymbol()`]: util.html#util_util_issymbol_object
[`util.isUndefined()`]: util.html#util_util_isundefined_object
[`util.log()`]: util.html#util_util_log_string
[`util.print()`]: util.html#util_util_print_strings
[`util.puts()`]: util.html#util_util_puts_strings
[`util`]: util.html
[`worker.exitedAfterDisconnect`]: cluster.html#cluster_worker_exitedafterdisconnect
[`worker.suicide`]: cluster.html#cluster_worker_suicide
[alloc]: buffer.html#buffer_class_method_buffer_alloc_size_fill_encoding
[alloc_unsafe_size]: buffer.html#buffer_class_method_buffer_allocunsafe_size
[from_arraybuffer]: buffer.html#buffer_class_method_buffer_from_arraybuffer_byteoffset_length
[from_string_encoding]: buffer.html#buffer_class_method_buffer_from_string_encoding
