# Settings

This is an exhaustive list of settings for Gunicorn. Some settings are
only able to be set from a configuration file. The setting name is what
should be used in the configuration file. The command line arguments are
listed as well for reference on setting at the command line.

::: note
::: title
Note
:::

Settings can be specified by using environment variable
`GUNICORN_CMD_ARGS`. All available command line arguments can be used.
For example, to specify the bind address and number of workers:

    $ GUNICORN_CMD_ARGS="--bind=127.0.0.1 --workers=3" gunicorn app:app

::: versionadded
19.7
:::
:::

## Config File

### `config`

**Command line:** `-c CONFIG` or `--config CONFIG`

**Default:** `'./gunicorn.conf.py'`

`The Gunicorn config file<configuration_file>`{.interpreted-text
role="ref"}.

A string of the form `PATH`, `file:PATH`, or `python:MODULE_NAME`.

Only has an effect when specified on the command line or as part of an
application specific configuration.

By default, a file named `gunicorn.conf.py` will be read from the same
directory where gunicorn is being run.

::: versionchanged
19.4 Loading the config from a Python module requires the `python:`
prefix.
:::

### `wsgi_app` {#wsgi-app}

**Default:** `None`

A WSGI application path in pattern `$(MODULE_NAME):$(VARIABLE_NAME)`.

::: versionadded
20.1.0
:::

## Debugging

### `reload`

**Command line:** `--reload`

**Default:** `False`

Restart workers when code changes.

This setting is intended for development. It will cause workers to be
restarted whenever application code changes.

The reloader is incompatible with application preloading. When using a
paste configuration be sure that the server block does not import any
application code or the reload will not work as designed.

The default behavior is to attempt inotify with a fallback to file
system polling. Generally, inotify should be preferred if available
because it consumes less system resources.

::: note
::: title
Note
:::

In order to use the inotify reloader, you must have the `inotify`
package installed.
:::

### `reload_engine` {#reload-engine}

**Command line:** `--reload-engine STRING`

**Default:** `'auto'`

The implementation that should be used to power
`reload`{.interpreted-text role="ref"}.

Valid engines are:

-   `'auto'`
-   `'poll'`
-   `'inotify'` (requires inotify)

::: versionadded
19.7
:::

### `reload_extra_files` {#reload-extra-files}

**Command line:** `--reload-extra-file FILES`

**Default:** `[]`

Extends `reload`{.interpreted-text role="ref"} option to also watch and
reload on additional files (e.g., templates, configurations,
specifications, etc.).

::: versionadded
19.8
:::

### `spew`

**Command line:** `--spew`

**Default:** `False`

Install a trace function that spews every line executed by the server.

This is the nuclear option.

### `check_config` {#check-config}

**Command line:** `--check-config`

**Default:** `False`

Check the configuration and exit. The exit status is 0 if the
configuration is correct, and 1 if the configuration is incorrect.

### `print_config` {#print-config}

**Command line:** `--print-config`

**Default:** `False`

Print the configuration settings as fully resolved. Implies
`check-config`{.interpreted-text role="ref"}.

## Logging

### `accesslog`

**Command line:** `--access-logfile FILE`

**Default:** `None`

The Access log file to write to.

`'-'` means log to stdout.

### `disable_redirect_access_to_syslog` {#disable-redirect-access-to-syslog}

**Command line:** `--disable-redirect-access-to-syslog`

**Default:** `False`

Disable redirect access logs to syslog.

::: versionadded
19.8
:::

### `access_log_format` {#access-log-format}

**Command line:** `--access-logformat STRING`

**Default:**
`'%(h)s %(l)s %(u)s %(t)s "%(r)s" %(s)s %(b)s "%(f)s" "%(a)s"'`

The access log format.

  Identifier    Description
  ------------- ---------------------------------------
  h             remote address
  l             `'-'`
  u             user name (if HTTP Basic auth used)
  t             date of the request
  r             status line (e.g. `GET / HTTP/1.1`)
  m             request method
  U             URL path without query string
  q             query string
  H             protocol
  s             status
  B             response length
  b             response length or `'-'` (CLF format)
  f             referrer (note: header is `referer`)
  a             user agent
  T             request time in seconds
  M             request time in milliseconds
  D             request time in microseconds
  L             request time in decimal seconds
  p             process ID
  {header}i     request header
  {header}o     response header
  {variable}e   environment variable

Use lowercase for header and environment variable names, and put
`{...}x` names inside `%(...)s`. For example:

    %({x-forwarded-for}i)s

### `errorlog`

**Command line:** `--error-logfile FILE` or `--log-file FILE`

**Default:** `'-'`

The Error log file to write to.

Using `'-'` for FILE makes gunicorn log to stderr.

::: versionchanged
19.2 Log to stderr by default.
:::

### `loglevel`

**Command line:** `--log-level LEVEL`

**Default:** `'info'`

The granularity of Error log outputs.

Valid level names are:

-   `'debug'`
-   `'info'`
-   `'warning'`
-   `'error'`
-   `'critical'`

### `capture_output` {#capture-output}

**Command line:** `--capture-output`

**Default:** `False`

Redirect stdout/stderr to specified file in `errorlog`{.interpreted-text
role="ref"}.

::: versionadded
19.6
:::

### `logger_class` {#logger-class}

**Command line:** `--logger-class STRING`

**Default:** `'gunicorn.glogging.Logger'`

The logger you want to use to log events in Gunicorn.

The default class (`gunicorn.glogging.Logger`) handles most normal
usages in logging. It provides error and access logging.

You can provide your own logger by giving Gunicorn a Python path to a
class that quacks like `gunicorn.glogging.Logger`.

### `logconfig`

**Command line:** `--log-config FILE`

**Default:** `None`

The log config file to use. Gunicorn uses the standard Python logging
module\'s Configuration file format.

### `logconfig_dict` {#logconfig-dict}

**Default:** `{}`

The log config dictionary to use, using the standard Python logging
module\'s dictionary configuration format. This option takes precedence
over the `logconfig`{.interpreted-text role="ref"} and
`logconfig-json`{.interpreted-text role="ref"} options, which uses the
older file configuration format and JSON respectively.

Format:
<https://docs.python.org/3/library/logging.config.html#logging.config.dictConfig>

For more context you can look at the default configuration dictionary
for logging, which can be found at `gunicorn.glogging.CONFIG_DEFAULTS`.

::: versionadded
19.8
:::

### `logconfig_json` {#logconfig-json}

**Command line:** `--log-config-json FILE`

**Default:** `None`

The log config to read config from a JSON file

Format:
<https://docs.python.org/3/library/logging.config.html#logging.config.jsonConfig>

::: versionadded
20.0
:::

### `syslog_addr` {#syslog-addr}

**Command line:** `--log-syslog-to SYSLOG_ADDR`

**Default:** `'unix:///var/run/syslog'`

Address to send syslog messages.

Address is a string of the form:

-   `unix://PATH#TYPE` : for unix domain socket. `TYPE` can be `stream`
    for the stream driver or `dgram` for the dgram driver. `stream` is
    the default.
-   `udp://HOST:PORT` : for UDP sockets
-   `tcp://HOST:PORT` : for TCP sockets

### `syslog`

**Command line:** `--log-syslog`

**Default:** `False`

Send *Gunicorn* logs to syslog.

::: versionchanged
19.8 You can now disable sending access logs by using the
`disable-redirect-access-to-syslog`{.interpreted-text role="ref"}
setting.
:::

### `syslog_prefix` {#syslog-prefix}

**Command line:** `--log-syslog-prefix SYSLOG_PREFIX`

**Default:** `None`

Makes Gunicorn use the parameter as program-name in the syslog entries.

All entries will be prefixed by `gunicorn.<prefix>`. By default the
program name is the name of the process.

### `syslog_facility` {#syslog-facility}

**Command line:** `--log-syslog-facility SYSLOG_FACILITY`

**Default:** `'user'`

Syslog facility name

### `enable_stdio_inheritance` {#enable-stdio-inheritance}

**Command line:** `-R` or `--enable-stdio-inheritance`

**Default:** `False`

Enable stdio inheritance.

Enable inheritance for stdio file descriptors in daemon mode.

Note: To disable the Python stdout buffering, you can to set the user
environment variable `PYTHONUNBUFFERED` .

### `statsd_host` {#statsd-host}

**Command line:** `--statsd-host STATSD_ADDR`

**Default:** `None`

The address of the StatsD server to log to.

Address is a string of the form:

-   `unix://PATH` : for a unix domain socket.
-   `HOST:PORT` : for a network address

::: versionadded
19.1
:::

### `dogstatsd_tags` {#dogstatsd-tags}

**Command line:** `--dogstatsd-tags DOGSTATSD_TAGS`

**Default:** `''`

A comma-delimited list of datadog statsd (dogstatsd) tags to append to
statsd metrics.

::: versionadded
20
:::

### `statsd_prefix` {#statsd-prefix}

**Command line:** `--statsd-prefix STATSD_PREFIX`

**Default:** `''`

Prefix to use when emitting statsd metrics (a trailing `.` is added, if
not provided).

::: versionadded
19.2
:::

## Process Naming

### `proc_name` {#proc-name}

**Command line:** `-n STRING` or `--name STRING`

**Default:** `None`

A base to use with setproctitle for process naming.

This affects things like `ps` and `top`. If you\'re going to be running
more than one instance of Gunicorn you\'ll probably want to set a name
to tell them apart. This requires that you install the setproctitle
module.

If not set, the *default_proc_name* setting will be used.

### `default_proc_name` {#default-proc-name}

**Default:** `'gunicorn'`

Internal setting that is adjusted for each type of application.

## SSL

### `keyfile`

**Command line:** `--keyfile FILE`

**Default:** `None`

SSL key file

### `certfile`

**Command line:** `--certfile FILE`

**Default:** `None`

SSL certificate file

### `ssl_version` {#ssl-version}

**Command line:** `--ssl-version`

**Default:** `<_SSLMethod.PROTOCOL_TLS: 2>`

SSL version to use (see stdlib ssl module\'s).

::: deprecated
21.0 The option is deprecated and it is currently ignored. Use
`ssl-context`{.interpreted-text role="ref"} instead.
:::

  \--ssl-version   Description
  ---------------- -------------------------------------------------------------------------------------------------------------------------
  SSLv3            SSLv3 is not-secure and is strongly discouraged.
  SSLv23           Alias for TLS. Deprecated in Python 3.6, use TLS.
  TLS              Negotiate highest possible version between client/server. Can yield SSL. (Python 3.6+)
  TLSv1            TLS 1.0
  TLSv1_1          TLS 1.1 (Python 3.4+)
  TLSv1_2          TLS 1.2 (Python 3.4+)
  TLS_SERVER       Auto-negotiate the highest protocol version like TLS, but only support server-side SSLSocket connections. (Python 3.6+)

::: versionchanged
19.7 The default value has been changed from `ssl.PROTOCOL_TLSv1` to
`ssl.PROTOCOL_SSLv23`.
:::

::: versionchanged
20.0 This setting now accepts string names based on `ssl.PROTOCOL_`
constants.
:::

::: versionchanged
20.0.1 The default value has been changed from `ssl.PROTOCOL_SSLv23` to
`ssl.PROTOCOL_TLS` when Python \>= 3.6 .
:::

### `cert_reqs` {#cert-reqs}

**Command line:** `--cert-reqs`

**Default:** `<VerifyMode.CERT_NONE: 0>`

Whether client certificate is required (see stdlib ssl module\'s)

  \--cert-reqs      Description
  ----------------- ------------------------
  [0]{.title-ref}   no client verification
  [1]{.title-ref}   ssl.CERT_OPTIONAL
  [2]{.title-ref}   ssl.CERT_REQUIRED

### `ca_certs` {#ca-certs}

**Command line:** `--ca-certs FILE`

**Default:** `None`

CA certificates file

### `suppress_ragged_eofs` {#suppress-ragged-eofs}

**Command line:** `--suppress-ragged-eofs`

**Default:** `True`

Suppress ragged EOFs (see stdlib ssl module\'s)

### `do_handshake_on_connect` {#do-handshake-on-connect}

**Command line:** `--do-handshake-on-connect`

**Default:** `False`

Whether to perform SSL handshake on socket connect (see stdlib ssl
module\'s)

### `ciphers`

**Command line:** `--ciphers`

**Default:** `None`

SSL Cipher suite to use, in the format of an OpenSSL cipher list.

By default we use the default cipher list from Python\'s `ssl` module,
which contains ciphers considered strong at the time of each Python
release.

As a recommended alternative, the Open Web App Security Project (OWASP)
offers [a vetted set of strong cipher strings rated A+ to
C-](https://www.owasp.org/index.php/TLS_Cipher_String_Cheat_Sheet).
OWASP provides details on user-agent compatibility at each security
level.

See the [OpenSSL Cipher List Format
Documentation](https://www.openssl.org/docs/manmaster/man1/ciphers.html#CIPHER-LIST-FORMAT)
for details on the format of an OpenSSL cipher list.

## Security

### `limit_request_line` {#limit-request-line}

**Command line:** `--limit-request-line INT`

**Default:** `4094`

The maximum size of HTTP request line in bytes.

This parameter is used to limit the allowed size of a client\'s HTTP
request-line. Since the request-line consists of the HTTP method, URI,
and protocol version, this directive places a restriction on the length
of a request-URI allowed for a request on the server. A server needs
this value to be large enough to hold any of its resource names,
including any information that might be passed in the query part of a
GET request. Value is a number from 0 (unlimited) to 8190.

This parameter can be used to prevent any DDOS attack.

### `limit_request_fields` {#limit-request-fields}

**Command line:** `--limit-request-fields INT`

**Default:** `100`

Limit the number of HTTP headers fields in a request.

This parameter is used to limit the number of headers in a request to
prevent DDOS attack. Used with the *limit_request_field_size* it allows
more safety. By default this value is 100 and can\'t be larger than
32768.

### `limit_request_field_size` {#limit-request-field-size}

**Command line:** `--limit-request-field_size INT`

**Default:** `8190`

Limit the allowed size of an HTTP request header field.

Value is a positive number or 0. Setting it to 0 will allow unlimited
header field sizes.

::: warning
::: title
Warning
:::

Setting this parameter to a very high or unlimited value can open up for
DDOS attacks.
:::

## Server Hooks

### `on_starting` {#on-starting}

**Default:**

``` python
def on_starting(server):
    pass
```

Called just before the master process is initialized.

The callable needs to accept a single instance variable for the Arbiter.

### `on_reload` {#on-reload}

**Default:**

``` python
def on_reload(server):
    pass
```

Called to recycle workers during a reload via SIGHUP.

The callable needs to accept a single instance variable for the Arbiter.

### `when_ready` {#when-ready}

**Default:**

``` python
def when_ready(server):
    pass
```

Called just after the server is started.

The callable needs to accept a single instance variable for the Arbiter.

### `pre_fork` {#pre-fork}

**Default:**

``` python
def pre_fork(server, worker):
    pass
```

Called just before a worker is forked.

The callable needs to accept two instance variables for the Arbiter and
new Worker.

### `post_fork` {#post-fork}

**Default:**

``` python
def post_fork(server, worker):
    pass
```

Called just after a worker has been forked.

The callable needs to accept two instance variables for the Arbiter and
new Worker.

### `post_worker_init` {#post-worker-init}

**Default:**

``` python
def post_worker_init(worker):
    pass
```

Called just after a worker has initialized the application.

The callable needs to accept one instance variable for the initialized
Worker.

### `worker_int` {#worker-int}

**Default:**

``` python
def worker_int(worker):
    pass
```

Called just after a worker exited on SIGINT or SIGQUIT.

The callable needs to accept one instance variable for the initialized
Worker.

### `worker_abort` {#worker-abort}

**Default:**

``` python
def worker_abort(worker):
    pass
```

Called when a worker received the SIGABRT signal.

This call generally happens on timeout.

The callable needs to accept one instance variable for the initialized
Worker.

### `pre_exec` {#pre-exec}

**Default:**

``` python
def pre_exec(server):
    pass
```

Called just before a new master process is forked.

The callable needs to accept a single instance variable for the Arbiter.

### `pre_request` {#pre-request}

**Default:**

``` python
def pre_request(worker, req):
    worker.log.debug("%s %s", req.method, req.path)
```

Called just before a worker processes the request.

The callable needs to accept two instance variables for the Worker and
the Request.

### `post_request` {#post-request}

**Default:**

``` python
def post_request(worker, req, environ, resp):
    pass
```

Called after a worker processes the request.

The callable needs to accept two instance variables for the Worker and
the Request.

### `child_exit` {#child-exit}

**Default:**

``` python
def child_exit(server, worker):
    pass
```

Called just after a worker has been exited, in the master process.

The callable needs to accept two instance variables for the Arbiter and
the just-exited Worker.

::: versionadded
19.7
:::

### `worker_exit` {#worker-exit}

**Default:**

``` python
def worker_exit(server, worker):
    pass
```

Called just after a worker has been exited, in the worker process.

The callable needs to accept two instance variables for the Arbiter and
the just-exited Worker.

### `nworkers_changed` {#nworkers-changed}

**Default:**

``` python
def nworkers_changed(server, new_value, old_value):
    pass
```

Called just after *num_workers* has been changed.

The callable needs to accept an instance variable of the Arbiter and two
integers of number of workers after and before change.

If the number of workers is set for the first time, *old_value* would be
`None`.

### `on_exit` {#on-exit}

**Default:**

``` python
def on_exit(server):
    pass
```

Called just before exiting Gunicorn.

The callable needs to accept a single instance variable for the Arbiter.

### `ssl_context` {#ssl-context}

**Default:**

``` python
def ssl_context(config, default_ssl_context_factory):
    return default_ssl_context_factory()
```

Called when SSLContext is needed.

Allows customizing SSL context.

The callable needs to accept an instance variable for the Config and a
factory function that returns default SSLContext which is initialized
with certificates, private key, cert_reqs, and ciphers according to
config and can be further customized by the callable. The callable needs
to return SSLContext object.

Following example shows a configuration file that sets the minimum TLS
version to 1.3:

``` python
def ssl_context(conf, default_ssl_context_factory):
    import ssl
    context = default_ssl_context_factory()
    context.minimum_version = ssl.TLSVersion.TLSv1_3
    return context
```

::: versionadded
21.0
:::

## Server Mechanics

### `preload_app` {#preload-app}

**Command line:** `--preload`

**Default:** `False`

Load application code before the worker processes are forked.

By preloading an application you can save some RAM resources as well as
speed up server boot times. Although, if you defer application loading
to each worker process, you can reload your application code easily by
restarting workers.

### `sendfile`

**Command line:** `--no-sendfile`

**Default:** `None`

Disables the use of `sendfile()`.

If not set, the value of the `SENDFILE` environment variable is used to
enable or disable its usage.

::: versionadded
19.2
:::

::: versionchanged
19.4 Swapped `--sendfile` with `--no-sendfile` to actually allow
disabling.
:::

::: versionchanged
19.6 added support for the `SENDFILE` environment variable
:::

### `reuse_port` {#reuse-port}

**Command line:** `--reuse-port`

**Default:** `False`

Set the `SO_REUSEPORT` flag on the listening socket.

::: versionadded
19.8
:::

### `chdir`

**Command line:** `--chdir`

**Default:** `'.'`

Change directory to specified directory before loading apps.

### `daemon`

**Command line:** `-D` or `--daemon`

**Default:** `False`

Daemonize the Gunicorn process.

Detaches the server from the controlling terminal and enters the
background.

### `raw_env` {#raw-env}

**Command line:** `-e ENV` or `--env ENV`

**Default:** `[]`

Set environment variables in the execution environment.

Should be a list of strings in the `key=value` format.

For example on the command line:

``` console
$ gunicorn -b 127.0.0.1:8000 --env FOO=1 test:app
```

Or in the configuration file:

``` python
raw_env = ["FOO=1"]
```

### `pidfile`

**Command line:** `-p FILE` or `--pid FILE`

**Default:** `None`

A filename to use for the PID file.

If not set, no PID file will be written.

### `worker_tmp_dir` {#worker-tmp-dir}

**Command line:** `--worker-tmp-dir DIR`

**Default:** `None`

A directory to use for the worker heartbeat temporary file.

If not set, the default temporary directory will be used.

::: note
::: title
Note
:::

The current heartbeat system involves calling `os.fchmod` on temporary
file handlers and may block a worker for arbitrary time if the directory
is on a disk-backed filesystem.

See `blocking-os-fchmod`{.interpreted-text role="ref"} for more detailed
information and a solution for avoiding this problem.
:::

### `user`

**Command line:** `-u USER` or `--user USER`

**Default:** `os.geteuid()`

Switch worker processes to run as this user.

A valid user id (as an integer) or the name of a user that can be
retrieved with a call to `pwd.getpwnam(value)` or `None` to not change
the worker process user.

### `group`

**Command line:** `-g GROUP` or `--group GROUP`

**Default:** `os.getegid()`

Switch worker process to run as this group.

A valid group id (as an integer) or the name of a user that can be
retrieved with a call to `grp.getgrnam(value)` or `None` to not change
the worker processes group.

### `umask`

**Command line:** `-m INT` or `--umask INT`

**Default:** `0`

A bit mask for the file mode on files written by Gunicorn.

Note that this affects unix socket permissions.

A valid value for the `os.umask(mode)` call or a string compatible with
`int(value, 0)` (`0` means Python guesses the base, so values like `0`,
`0xFF`, `0022` are valid for decimal, hex, and octal representations)

### `initgroups`

**Command line:** `--initgroups`

**Default:** `False`

If true, set the worker process\'s group access list with all of the
groups of which the specified username is a member, plus the specified
group id.

::: versionadded
19.7
:::

### `tmp_upload_dir` {#tmp-upload-dir}

**Default:** `None`

Directory to store temporary request data as they are read.

This may disappear in the near future.

This path should be writable by the process permissions set for Gunicorn
workers. If not specified, Gunicorn will choose a system generated
temporary directory.

### `secure_scheme_headers` {#secure-scheme-headers}

**Default:**
`{'X-FORWARDED-PROTOCOL': 'ssl', 'X-FORWARDED-PROTO': 'https', 'X-FORWARDED-SSL': 'on'}`

A dictionary containing headers and values that the front-end proxy uses
to indicate HTTPS requests. If the source IP is permitted by
`forwarded-allow-ips`{.interpreted-text role="ref"} (below), *and* at
least one request header matches a key-value pair listed in this
dictionary, then Gunicorn will set `wsgi.url_scheme` to `https`, so your
application can tell that the request is secure.

If the other headers listed in this dictionary are not present in the
request, they will be ignored, but if the other headers are present and
do not match the provided values, then the request will fail to parse.
See the note below for more detailed examples of this behaviour.

The dictionary should map upper-case header names to exact string
values. The value comparisons are case-sensitive, unlike the header
names, so make sure they\'re exactly what your front-end proxy sends
when handling HTTPS requests.

It is important that your front-end proxy configuration ensures that the
headers defined here can not be passed directly from the client.

### `forwarded_allow_ips` {#forwarded-allow-ips}

**Command line:** `--forwarded-allow-ips STRING`

**Default:** `'127.0.0.1,::1'`

Front-end\'s IPs from which allowed to handle set secure headers. (comma
separated).

Set to `*` to disable checking of front-end IPs. This is useful for
setups where you don\'t know in advance the IP address of front-end, but
instead have ensured via other means that only your authorized
front-ends can access Gunicorn.

By default, the value of the `FORWARDED_ALLOW_IPS` environment variable.
If it is not defined, the default is `"127.0.0.1,::1"`.

::: note
::: title
Note
:::

This option does not affect UNIX socket connections. Connections not
associated with an IP address are treated as allowed, unconditionally.
:::

::: note
::: title
Note
:::

The interplay between the request headers, the value of
`forwarded_allow_ips`, and the value of `secure_scheme_headers` is
complex. Various scenarios are documented below to further elaborate. In
each case, we have a request from the remote address 134.213.44.18, and
the default value of `secure_scheme_headers`:

``` 
secure_scheme_headers = {
    'X-FORWARDED-PROTOCOL': 'ssl',
    'X-FORWARDED-PROTO': 'https',
    'X-FORWARDED-SSL': 'on'
}
```

+----------------+----------------+----------------+----------------+
| `forwar        | Secure Request | Result         | Explanation    |
| ded-allow-ips` | Headers        |                |                |
+================+================+================+================+
| ```            | ```            | ```            | IP address was |
| ["127.0.0.1"]  | X-Forwarde     | wsgi.url_s     | not allowed    |
| ```            | d-Proto: https | cheme = "http" |                |
|                | ```            | ```            |                |
+----------------+----------------+----------------+----------------+
| ```            | \<none\>       | ```            | IP address     |
| "*"            |                | wsgi.url_s     | allowed, but   |
| ```            |                | cheme = "http" | no secure      |
|                |                | ```            | headers        |
|                |                |                | provided       |
+----------------+----------------+----------------+----------------+
| ```            | ```            | ```            | IP address     |
| "*"            | X-Forwarde     | wsgi.url_sc    | allowed, one   |
| ```            | d-Proto: https | heme = "https" | request header |
|                | ```            | ```            | matched        |
+----------------+----------------+----------------+----------------+
| ```            | ```            | `InvalidSc     | IP address     |
| ["1            | X-For          | hemeHeaders()` | allowed, but   |
| 34.213.44.18"] | warded-Ssl: on | raised         | the two secure |
| ```            | X-Forward      |                | headers        |
|                | ed-Proto: http |                | disagreed on   |
|                | ```            |                | if HTTPS was   |
|                |                |                | used           |
+----------------+----------------+----------------+----------------+
:::

### `pythonpath`

**Command line:** `--pythonpath STRING`

**Default:** `None`

A comma-separated list of directories to add to the Python path.

e.g. `'/home/djangoprojects/myproject,/home/python/mylibrary'`.

### `paste`

**Command line:** `--paste STRING` or `--paster STRING`

**Default:** `None`

Load a PasteDeploy config file. The argument may contain a `#` symbol
followed by the name of an app section from the config file, e.g.
`production.ini#admin`.

At this time, using alternate server blocks is not supported. Use the
command line arguments to control server configuration instead.

### `proxy_protocol` {#proxy-protocol}

**Command line:** `--proxy-protocol`

**Default:** `False`

Enable detect PROXY protocol (PROXY mode).

Allow using HTTP and Proxy together. It may be useful for work with
stunnel as HTTPS frontend and Gunicorn as HTTP server.

PROXY protocol:
<http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt>

Example for stunnel config:

    [https]
    protocol = proxy
    accept  = 443
    connect = 80
    cert = /etc/ssl/certs/stunnel.pem
    key = /etc/ssl/certs/stunnel.key

### `proxy_allow_ips` {#proxy-allow-ips}

**Command line:** `--proxy-allow-from`

**Default:** `'127.0.0.1,::1'`

Front-end\'s IPs from which allowed accept proxy requests (comma
separated).

Set to `*` to disable checking of front-end IPs. This is useful for
setups where you don\'t know in advance the IP address of front-end, but
instead have ensured via other means that only your authorized
front-ends can access Gunicorn.

::: note
::: title
Note
:::

This option does not affect UNIX socket connections. Connections not
associated with an IP address are treated as allowed, unconditionally.
:::

### `raw_paste_global_conf` {#raw-paste-global-conf}

**Command line:** `--paste-global CONF`

**Default:** `[]`

Set a PasteDeploy global config variable in `key=value` form.

The option can be specified multiple times.

The variables are passed to the PasteDeploy entrypoint. Example:

    $ gunicorn -b 127.0.0.1:8000 --paste development.ini --paste-global FOO=1 --paste-global BAR=2

::: versionadded
19.7
:::

### `permit_obsolete_folding` {#permit-obsolete-folding}

**Command line:** `--permit-obsolete-folding`

**Default:** `False`

Permit requests employing obsolete HTTP line folding mechanism

The folding mechanism was deprecated by rfc7230 Section 3.2.4 and will not be

:   employed in HTTP request headers from standards-compliant HTTP
    clients.

This option is provided to diagnose backwards-incompatible changes. Use
with care and only if necessary. Temporary; the precise effect of this
option may change in a future version, or it may be removed altogether.

::: versionadded
23.0.0
:::

### `strip_header_spaces` {#strip-header-spaces}

**Command line:** `--strip-header-spaces`

**Default:** `False`

Strip spaces present between the header name and the the `:`.

This is known to induce vulnerabilities and is not compliant with the
HTTP/1.1 standard. See
<https://portswigger.net/research/http-desync-attacks-request-smuggling-reborn>.

Use with care and only if necessary. Deprecated; scheduled for removal
in 25.0.0

::: versionadded
20.0.1
:::

### `permit_unconventional_http_method` {#permit-unconventional-http-method}

**Command line:** `--permit-unconventional-http-method`

**Default:** `False`

Permit HTTP methods not matching conventions, such as IANA registration
guidelines

This permits request methods of length less than 3 or more than 20,
methods with lowercase characters or methods containing the \#
character. HTTP methods are case sensitive by definition, and merely
uppercase by convention.

If unset, Gunicorn will apply nonstandard restrictions and cause 400
response status in cases where otherwise 501 status is expected. While
this option does modify that behaviour, it should not be depended upon
to guarantee standards-compliant behaviour. Rather, it is provided
temporarily, to assist in diagnosing backwards-incompatible changes
around the incomplete application of those restrictions.

Use with care and only if necessary. Temporary; scheduled for removal in
24.0.0

::: versionadded
22.0.0
:::

### `permit_unconventional_http_version` {#permit-unconventional-http-version}

**Command line:** `--permit-unconventional-http-version`

**Default:** `False`

Permit HTTP version not matching conventions of 2023

This disables the refusal of likely malformed request lines. It is
unusual to specify HTTP 1 versions other than 1.0 and 1.1.

This option is provided to diagnose backwards-incompatible changes. Use
with care and only if necessary. Temporary; the precise effect of this
option may change in a future version, or it may be removed altogether.

::: versionadded
22.0.0
:::

### `casefold_http_method` {#casefold-http-method}

**Command line:** `--casefold-http-method`

**Default:** `False`

Transform received HTTP methods to uppercase

HTTP methods are case sensitive by definition, and merely uppercase by
convention.

This option is provided because previous versions of gunicorn defaulted
to this behaviour.

Use with care and only if necessary. Deprecated; scheduled for removal
in 24.0.0

::: versionadded
22.0.0
:::

### `forwarder_headers` {#forwarder-headers}

**Command line:** `--forwarder-headers`

**Default:** `'SCRIPT_NAME,PATH_INFO'`

A list containing upper-case header field names that the front-end proxy
(see `forwarded-allow-ips`{.interpreted-text role="ref"}) sets, to be
used in WSGI environment.

This option has no effect for headers not present in the request.

This option can be used to transfer `SCRIPT_NAME`, `PATH_INFO` and
`REMOTE_USER`.

It is important that your front-end proxy configuration ensures that the
headers defined here can not be passed directly from the client.

### `header_map` {#header-map}

**Command line:** `--header-map`

**Default:** `'drop'`

Configure how header field names are mapped into environ

Headers containing underscores are permitted by RFC9110, but gunicorn
joining headers of different names into the same environment variable
will dangerously confuse applications as to which is which.

The safe default `drop` is to silently drop headers that cannot be
unambiguously mapped. The value `refuse` will return an error if a
request contains *any* such header. The value `dangerous` matches the
previous, not advisable, behaviour of mapping different header field
names into the same environ name.

If the source is permitted as explained in
`forwarded-allow-ips`{.interpreted-text role="ref"}, *and* the header
name is present in `forwarder-headers`{.interpreted-text role="ref"},
the header is mapped into environment regardless of the state of this
setting.

Use with care and only if necessary and after considering if your
problem could instead be solved by specifically renaming or rewriting
only the intended headers on a proxy in front of Gunicorn.

::: versionadded
22.0.0
:::

## Server Socket

### `bind`

**Command line:** `-b ADDRESS` or `--bind ADDRESS`

**Default:** `['127.0.0.1:8000']`

The socket to bind.

A string of the form: `HOST`, `HOST:PORT`, `unix:PATH`, `fd://FD`. An IP
is a valid `HOST`.

::: versionchanged
20.0 Support for `fd://FD` got added.
:::

Multiple addresses can be bound. ex.:

    $ gunicorn -b 127.0.0.1:8000 -b [::1]:8000 test:app

will bind the [test:app]{.title-ref} application on localhost both on
ipv6 and ipv4 interfaces.

If the `PORT` environment variable is defined, the default is
`['0.0.0.0:$PORT']`. If it is not defined, the default is
`['127.0.0.1:8000']`.

### `backlog`

**Command line:** `--backlog INT`

**Default:** `2048`

The maximum number of pending connections.

This refers to the number of clients that can be waiting to be served.
Exceeding this number results in the client getting an error when
attempting to connect. It should only affect servers under significant
load.

Must be a positive integer. Generally set in the 64-2048 range.

## Worker Processes

### `workers`

**Command line:** `-w INT` or `--workers INT`

**Default:** `1`

The number of worker processes for handling requests.

A positive integer generally in the `2-4 x $(NUM_CORES)` range. You\'ll
want to vary this a bit to find the best for your particular
application\'s work load.

By default, the value of the `WEB_CONCURRENCY` environment variable,
which is set by some Platform-as-a-Service providers such as Heroku. If
it is not defined, the default is `1`.

### `worker_class` {#worker-class}

**Command line:** `-k STRING` or `--worker-class STRING`

**Default:** `'sync'`

The type of workers to use.

The default class (`sync`) should handle most \"normal\" types of
workloads. You\'ll want to read `design`{.interpreted-text role="doc"}
for information on when you might want to choose one of the other worker
classes. Required libraries may be installed using setuptools\'
`extras_require` feature.

A string referring to one of the following bundled classes:

-   `sync`
-   `eventlet` - Requires eventlet \>= 0.24.1 (or install it via
    `pip install gunicorn[eventlet]`)
-   `gevent` - Requires gevent \>= 1.4 (or install it via
    `pip install gunicorn[gevent]`)
-   `tornado` - Requires tornado \>= 0.2 (or install it via
    `pip install gunicorn[tornado]`)
-   `gthread` - Python 2 requires the futures package to be installed
    (or install it via `pip install gunicorn[gthread]`)

Optionally, you can provide your own worker by giving Gunicorn a Python
path to a subclass of `gunicorn.workers.base.Worker`. This alternative
syntax will load the gevent class:
`gunicorn.workers.ggevent.GeventWorker`.

### `threads`

**Command line:** `--threads INT`

**Default:** `1`

The number of worker threads for handling requests.

Run each worker with the specified number of threads.

A positive integer generally in the `2-4 x $(NUM_CORES)` range. You\'ll
want to vary this a bit to find the best for your particular
application\'s work load.

If it is not defined, the default is `1`.

This setting only affects the Gthread worker type.

::: note
::: title
Note
:::

If you try to use the `sync` worker type and set the `threads` setting
to more than 1, the `gthread` worker type will be used instead.
:::

### `worker_connections` {#worker-connections}

**Command line:** `--worker-connections INT`

**Default:** `1000`

The maximum number of simultaneous clients.

This setting only affects the `gthread`, `eventlet` and `gevent` worker
types.

### `max_requests` {#max-requests}

**Command line:** `--max-requests INT`

**Default:** `0`

The maximum number of requests a worker will process before restarting.

Any value greater than zero will limit the number of requests a worker
will process before automatically restarting. This is a simple method to
help limit the damage of memory leaks.

If this is set to zero (the default) then the automatic worker restarts
are disabled.

### `max_requests_jitter` {#max-requests-jitter}

**Command line:** `--max-requests-jitter INT`

**Default:** `0`

The maximum jitter to add to the *max_requests* setting.

The jitter causes the restart per worker to be randomized by
`randint(0, max_requests_jitter)`. This is intended to stagger worker
restarts to avoid all workers restarting at the same time.

::: versionadded
19.2
:::

### `timeout`

**Command line:** `-t INT` or `--timeout INT`

**Default:** `30`

Workers silent for more than this many seconds are killed and restarted.

Value is a positive number or 0. Setting it to 0 has the effect of
infinite timeouts by disabling timeouts for all workers entirely.

Generally, the default of thirty seconds should suffice. Only set this
noticeably higher if you\'re sure of the repercussions for sync workers.
For the non sync workers it just means that the worker process is still
communicating and is not tied to the length of time required to handle a
single request.

### `graceful_timeout` {#graceful-timeout}

**Command line:** `--graceful-timeout INT`

**Default:** `30`

Timeout for graceful workers restart in seconds.

After receiving a restart signal, workers have this much time to finish
serving requests. Workers still alive after the timeout (starting from
the receipt of the restart signal) are force killed.

### `keepalive`

**Command line:** `--keep-alive INT`

**Default:** `2`

The number of seconds to wait for requests on a Keep-Alive connection.

Generally set in the 1-5 seconds range for servers with direct
connection to the client (e.g. when you don\'t have separate load
balancer). When Gunicorn is deployed behind a load balancer, it often
makes sense to set this to a higher value.

::: note
::: title
Note
:::

`sync` worker does not support persistent connections and will ignore
this option.
:::