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Settings

Use the following options to configure Uvicorn, when running from the command line.

If you're running programmatically, using uvicorn.run(...), then use equivalent keyword arguments, eg. uvicorn.run("example:app", port=5000, reload=True, access_log=False). Please note that in this case, if you use reload=True or workers=NUM, you should put uvicorn.run into if __name__ == '__main__' clause in the main module.

You can also configure Uvicorn using environment variables with the prefix UVICORN_. For example, in case you want to run the app on port 5000, just set the environment variable UVICORN_PORT to 5000.

Note

CLI options and the arguments for uvicorn.run() take precedence over environment variables.

Also note that UVICORN_* prefixed settings cannot be used from within an environment configuration file. Using an environment configuration file with the --env-file flag is intended for configuring the ASGI application that uvicorn runs, rather than configuring uvicorn itself.

Application

  • APP - The ASGI application to run, in the format "<module>:<attribute>".
  • --factory - Treat APP as an application factory, i.e. a () -> <ASGI app> callable.

Socket Binding

  • --host <str> - Bind socket to this host. Use --host 0.0.0.0 to make the application available on your local network. IPv6 addresses are supported, for example: --host '::'. Default: '127.0.0.1'.
  • --port <int> - Bind to a socket with this port. Default: 8000.
  • --uds <path> - Bind to a UNIX domain socket, for example --uds /tmp/uvicorn.sock. Useful if you want to run Uvicorn behind a reverse proxy.
  • --fd <int> - Bind to socket from this file descriptor. Useful if you want to run Uvicorn within a process manager.

Development

  • --reload - Enable auto-reload. Uvicorn supports two versions of auto-reloading behavior enabled by this option. There are important differences between them.
  • --reload-dir <path> - Specify which directories to watch for python file changes. May be used multiple times. If unused, then by default the whole current directory will be watched. If you are running programmatically use reload_dirs=[] and pass a list of strings.

Reloading without watchfiles

If Uvicorn cannot load watchfiles at runtime, it will periodically look for changes in modification times to all *.py files (and only *.py files) inside of its monitored directories. See the --reload-dir option. Specifying other file extensions is not supported unless watchfiles is installed. See the --reload-include and --reload-exclude options for details.

Reloading with watchfiles

For more nuanced control over which file modifications trigger reloads, install uvicorn[standard], which includes watchfiles as a dependency. Alternatively, install watchfiles where Uvicorn can see it.

Using Uvicorn with watchfiles will enable the following options (which are otherwise ignored).

  • --reload-include <glob-pattern> - Specify a glob pattern to match files or directories which will be watched. May be used multiple times. By default the following patterns are included: *.py. These defaults can be overwritten by including them in --reload-exclude.
  • --reload-exclude <glob-pattern> - Specify a glob pattern to match files or directories which will excluded from watching. May be used multiple times. By default the following patterns are excluded: .*, .py[cod], .sw.*, ~*. These defaults can be overwritten by including them in --reload-include.

Tip

When using Uvicorn through WSL, you might have to set the WATCHFILES_FORCE_POLLING environment variable, for file changes to trigger a reload. See watchfiles documentation for further details.

Production

  • --workers <int> - Use multiple worker processes. Defaults to the $WEB_CONCURRENCY environment variable if available, or 1.

Logging

  • --log-config <path> - Logging configuration file. Options: dictConfig() formats: .json, .yaml. Any other format will be processed with fileConfig(). Set the formatters.default.use_colors and formatters.access.use_colors values to override the auto-detected behavior.
    • If you wish to use a YAML file for your logging config, you will need to include PyYAML as a dependency for your project or install uvicorn with the [standard] optional extras.
  • --log-level <str> - Set the log level. Options: 'critical', 'error', 'warning', 'info', 'debug', 'trace'. Default: 'info'.
  • --no-access-log - Disable access log only, without changing log level.
  • --use-colors / --no-use-colors - Enable / disable colorized formatting of the log records, in case this is not set it will be auto-detected. This option is ignored if the --log-config CLI option is used.

Implementation

  • --loop <str> - Set the event loop implementation. The uvloop implementation provides greater performance, but is not compatible with Windows or PyPy. Options: 'auto', 'asyncio', 'uvloop'. Default: 'auto'.
  • --http <str> - Set the HTTP protocol implementation. The httptools implementation provides greater performance, but it not compatible with PyPy. Options: 'auto', 'h11', 'httptools'. Default: 'auto'.
  • --ws <str> - Set the WebSockets protocol implementation. Either of the websockets and wsproto packages are supported. Use 'none' to ignore all websocket requests. Options: 'auto', 'none', 'websockets', 'wsproto'. Default: 'auto'.
  • --ws-max-size <int> - Set the WebSockets max message size, in bytes. Please note that this can be used only with the default websockets protocol.
  • --ws-ping-interval <float> - Set the WebSockets ping interval, in seconds. Please note that this can be used only with the default websockets protocol.
  • --ws-ping-timeout <float> - Set the WebSockets ping timeout, in seconds. Please note that this can be used only with the default websockets protocol.
  • --lifespan <str> - Set the Lifespan protocol implementation. Options: 'auto', 'on', 'off'. Default: 'auto'.
  • --h11-max-incomplete-event-size <int> - Set the maximum number of bytes to buffer of an incomplete event. Only available for h11 HTTP protocol implementation. Default: '16384' (16 KB).

Application Interface

  • --interface - Select ASGI3, ASGI2, or WSGI as the application interface. Note that WSGI mode always disables WebSocket support, as it is not supported by the WSGI interface. Options: 'auto', 'asgi3', 'asgi2', 'wsgi'. Default: 'auto'.

HTTP

  • --root-path <str> - Set the ASGI root_path for applications submounted below a given URL path.
  • --proxy-headers / --no-proxy-headers - Enable/Disable X-Forwarded-Proto, X-Forwarded-For, X-Forwarded-Port to populate remote address info. Defaults to enabled, but is restricted to only trusting connecting IPs in the forwarded-allow-ips configuration.
  • --forwarded-allow-ips Comma separated list of IPs to trust with proxy headers. Defaults to the $FORWARDED_ALLOW_IPS environment variable if available, or '127.0.0.1'. A wildcard '*' means always trust.
  • --server-header / --no-server-header - Enable/Disable default Server header.
  • --date-header / --no-date-header - Enable/Disable default Date header.

Note

The --no-date-header flag doesn't have effect on the websockets implementation.

HTTPS

  • --ssl-keyfile <path> - SSL key file
  • --ssl-keyfile-password <str> - Password to decrypt the ssl key
  • --ssl-certfile <path> - SSL certificate file
  • --ssl-version <int> - SSL version to use (see stdlib ssl module's)
  • --ssl-cert-reqs <int> - Whether client certificate is required (see stdlib ssl module's)
  • --ssl-ca-certs <str> - CA certificates file
  • --ssl-ciphers <str> - Ciphers to use (see stdlib ssl module's)

Resource Limits

  • --limit-concurrency <int> - Maximum number of concurrent connections or tasks to allow, before issuing HTTP 503 responses. Useful for ensuring known memory usage patterns even under over-resourced loads.
  • --limit-max-requests <int> - Maximum number of requests to service before terminating the process. Useful when running together with a process manager, for preventing memory leaks from impacting long-running processes.
  • --backlog <int> - Maximum number of connections to hold in backlog. Relevant for heavy incoming traffic. Default: 2048

Timeouts

  • --timeout-keep-alive <int> - Close Keep-Alive connections if no new data is received within this timeout. Default: 5.