# Running Sanic

Sanic ships with its own internal web server. Under most circumstances, this is the preferred method for deployment. In addition, you can also deploy Sanic as an ASGI app bundled with an ASGI-able web server, or using gunicorn.

# Sanic Server

After defining an instance of sanic.Sanic, we can call the run method with the following keyword arguments:

Parameter Default Description
host "" Address to host the server on.
port 8000 Port to host the server on.
unix None Unix socket name to host the server on (instead of TCP).
debug False Enables debug output (slows server).
ssl None SSLContext for SSL encryption of worker(s).
sock None Socket for the server to accept connections from.
workers 1 Number of worker processes to spawn.
loop None An asyncio-compatible event loop. If none is specified, Sanic creates its own event loop.
protocol HttpProtocol Subclass of asyncio.protocol.
access_log True Enables log on handling requests (significantly slows server).

In the above example, we decided to turn off the access log in order to increase performance.

# server.py
app = Sanic("My App")
app.run(host='', port=1337, access_log=False)

Now, just execute the python script that has app.run(...)

python server.py

# Workers

By default, Sanic listens in the main process using only one CPU core. To crank up the juice, just specify the number of workers in the run arguments.

app.run(host='', port=1337, workers=4)

Sanic will automatically spin up multiple processes and route traffic between them. We recommend as many workers as you have available processors.

The easiest way to get the maximum CPU performance is to use the fast option. This will automatically run the maximum number of workers given the system constraints.

app.run(host='', port=1337, fast=True)
$ sanic server:app --host= --port=1337 --fast

In older versions of Sanic without the fast option, a common way to check this on Linux based operating systems:

$ nproc

Or, let Python do it:

import multiprocessing
workers = multiprocessing.cpu_count()
app.run(..., workers=workers)

# Running via command

# Sanic CLI

Sanic also has a simple CLI to launch via command line.

For example, if you initialized Sanic as app in a file named server.py, you could run the server like so:

sanic server.app --host= --port=1337 --workers=4

Use sanic --help to see all the options.

$ sanic --help
usage: sanic [-h] [--version] [--factory] [-s] [-H HOST] [-p PORT] [-u UNIX] [--cert CERT] [--key KEY] [--tls DIR] [--tls-strict-host]
             [-w WORKERS | --fast] [--access-logs | --no-access-logs] [--debug] [-d] [-r] [-R PATH] [--motd | --no-motd] [-v]
             [--noisy-exceptions | --no-noisy-exceptions]
   ▄███ █████ ██      ▄█▄      ██       █   █   ▄██████████
  ██                 █   █     █ ██     █   █  ██
   ▀███████ ███▄    ▀     █    █   ██   ▄   █  ██
               ██  █████████   █     ██ █   █  ▄▄
  ████ ████████▀  █         █  █       ██   █   ▀██ ███████
 To start running a Sanic application, provide a path to the module, where
 app is a Sanic() instance:
     $ sanic path.to.server:app
 Or, a path to a callable that returns a Sanic() instance:
     $ sanic path.to.factory:create_app --factory
 Or, a path to a directory to run as a simple HTTP server:
     $ sanic ./path/to/static --simple
    module                         Path to your Sanic app. Example: path.to.server:app
                                   If running a Simple Server, path to directory to serve. Example: ./
    -h, --help                     show this help message and exit
    --version                      show program's version number and exit
    --factory                      Treat app as an application factory, i.e. a () -> <Sanic app> callable
    -s, --simple                   Run Sanic as a Simple Server, and serve the contents of a directory
                                   (module arg should be a path)
  Socket binding:
    -H HOST, --host HOST           Host address [default]
    -p PORT, --port PORT           Port to serve on [default 8000]
    -u UNIX, --unix UNIX           location of unix socket
  TLS certificate:
    --cert CERT                    Location of fullchain.pem, bundle.crt or equivalent
    --key KEY                      Location of privkey.pem or equivalent .key file
    --tls DIR                      TLS certificate folder with fullchain.pem and privkey.pem
                                   May be specified multiple times to choose multiple certificates
    --tls-strict-host              Only allow clients that send an SNI matching server certs
    -w WORKERS, --workers WORKERS  Number of worker processes [default 1]
    --fast                         Set the number of workers to max allowed
    --access-logs                  Display access logs
    --no-access-logs               No display access logs
    --debug                        Run the server in debug mode
    -d, --dev                      Currently is an alias for --debug. But starting in v22.3, 
                                   --debug will no longer automatically trigger auto_restart. 
                                   However, --dev will continue, effectively making it the 
                                   same as debug + auto_reload.
    -r, --reload, --auto-reload    Watch source directory for file changes and reload on changes
    -R PATH, --reload-dir PATH     Extra directories to watch and reload on changes
    --motd                         Show the startup display
    --no-motd                      No show the startup display
    -v, --verbosity                Control logging noise, eg. -vv or --verbosity=2 [default 0]
    --noisy-exceptions             Output stack traces for all exceptions
    --no-noisy-exceptions          No output stack traces for all exceptions

# As a module

It can also be called directly as a module.

python -m sanic server.app --host= --port=1337 --workers=4


With either method (CLI or module), you shoud not invoke app.run() in your Python file. If you do, make sure you wrap it so that it only executes when directly run by the interpreter.

if __name__ == '__main__':
    app.run(host='', port=1337, workers=4)

# Sanic Simple Server

Sometimes you just have a directory of static files that need to be served. This especially can be handy for quickly standing up a localhost server. Sanic ships with a Simple Server, where you only need to point it at a directory.

sanic ./path/to/dir --simple

This could also be paired with auto-reloading.

sanic ./path/to/dir --simple --reload --reload-dir=./path/to/dir

NEW in v22.6

# HTTP/3

Sanic server offers HTTP/3 support using aioquic (opens new window). This must be installed to use HTTP/3:

pip install sanic aioquic
pip install sanic[http3]

To start HTTP/3, you must explicitly request it when running your application.

$ sanic path.to.server:app --http=3
$ sanic path.to.server:app -3

To run both an HTTP/3 and HTTP/1.1 server simultaneously, you can use application multi-serve introduced in v22.3. This will automatically add an Alt-Svc (opens new window) header to your HTTP/1.1 requests to let the client know that it is also available as HTTP/3.

$ sanic path.to.server:app --http=3 --http=1
$ sanic path.to.server:app -3 -1

Because HTTP/3 requires TLS, you cannot start a HTTP/3 server without a TLS certificate. You should set it up yourself or use mkcert if in DEBUG mode. Currently, automatic TLS setup for HTTP/3 is not compatible with trustme. See development for more details.


Sanic is also ASGI-compliant. This means you can use your preferred ASGI webserver to run Sanic. The three main implementations of ASGI are Daphne (opens new window), Uvicorn (opens new window), and Hypercorn (opens new window).


Daphne does not support the ASGI lifespan protocol, and therefore cannot be used to run Sanic. See Issue #264 (opens new window) for more details.

Follow their documentation for the proper way to run them, but it should look something like:

uvicorn myapp:app
hypercorn myapp:app

A couple things to note when using ASGI:

  1. When using the Sanic webserver, websockets will run using the websockets package. In ASGI mode, there is no need for this package since websockets are managed in the ASGI server.
  2. The ASGI lifespan protocol https://asgi.readthedocs.io/en/latest/specs/lifespan.html (opens new window), supports only two server events: startup and shutdown. Sanic has four: before startup, after startup, before shutdown, and after shutdown. Therefore, in ASGI mode, the startup and shutdown events will run consecutively and not actually around the server process beginning and ending (since that is now controlled by the ASGI server). Therefore, it is best to use after_server_start and before_server_stop.

# Trio

Sanic has experimental support for running on Trio with:

hypercorn -k trio myapp:app

# Gunicorn

Gunicorn (opens new window) ("Green Unicorn") is a WSGI HTTP Server for UNIX based operating systems. It is a pre-fork worker model ported from Ruby’s Unicorn project.

In order to run Sanic application with Gunicorn, you need to use the special sanic.worker.GunicornWorker for Gunicorn worker-class argument:

gunicorn myapp:app --bind --worker-class sanic.worker.GunicornWorker

If your application suffers from memory leaks, you can configure Gunicorn to gracefully restart a worker after it has processed a given number of requests. This can be a convenient way to help limit the effects of the memory leak.

See the Gunicorn Docs (opens new window) for more information.


When running Sanic via gunicorn, you are losing out on a lot of the performance benefits of async/await. Weigh your considerations carefully before making this choice. Gunicorn does provide a lot of configuration options, but it is not the best choice for getting Sanic to run at its fastest.

# Performance considerations

When running in production, make sure you turn off debug.

app.run(..., debug=False)

Sanic will also perform fastest if you turn off access_log.

If you still require access logs, but want to enjoy this performance boost, consider using Nginx as a proxy, and letting that handle your access logging. It will be much faster than anything Python can handle.

app.run(..., access_log=False)
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Copyright © 2018-present Sanic Community Organization

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