# Development

The first thing that should be mentioned is that the webserver that is integrated into Sanic is not just a development server.

It is production ready out-of-the-box, unless you enable in debug mode.

# Debug mode

By setting the debug mode, Sanic will be more verbose in its output and will disable several run-time optimizations.

from sanic import Sanic
from sanic.response import json
app = Sanic(__name__)
async def hello_world(request):
    return json({"hello": "world"})
if __name__ == "__main__":
    app.run(host="", port=1234, debug=True)


Sanic's debug mode will slow down the server's performance and is therefore advised to enable it only in development environments.

# Automatic Reloader

Sanic offers a way to enable or disable the Automatic Reloader. The auto_reload argument will activate or deactivate the Automatic Reloader. Every time a Python file is changed, the reloader will restart your application automatically. This is very convenient while developing.


If you have additional directories that you would like to automatically reload on file save (for example, a directory of HTML templates), you can add that at run time.

app.run(auto_reload=True, reload_dir="/path/to/templates")
# or multiple directories
app.run(auto_reload=True, reload_dir=["/path/to/one", "/path/to/two"])

# Best of both worlds

If you would like to be in debug mode and have the Automatic Reloader running, you can pass dev=True. This is equivalent to debug + auto reload.

Added in v22.3


# Automatic TLS certificate

When running in DEBUG mode, you can ask Sanic to handle setting up localhost temporary TLS certificates. This is helpful if you want to access your local development environment with https://.

This functionality is provided by either mkcert (opens new window) or trustme (opens new window). Both are good choices, but there are some differences. trustme is a Python library and can be installed into your environment with pip. This makes for easy envrionment handling, but it is not compatible when running a HTTP/3 server. mkcert might be a more involved installation process, but can install a local CA and make it easier to use.

You can choose which platform to use by setting config.LOCAL_CERT_CREATOR. When set to "auto", it will select either option, preferring mkcert if possible.

app.config.LOCAL_CERT_CREATOR = "auto"
app.config.LOCAL_CERT_CREATOR = "mkcert"
app.config.LOCAL_CERT_CREATOR = "trustme"

Automatic TLS can be enabled at Sanic server run time:

$ sanic path.to.server:app --auto-tls --debug
app.run(debug=True, auto_tls=True)


Localhost TLS certificates (like those generated by both mkcert and trustme) are NOT suitable for production environments. If you are not familiar with how to obtain a real TLS certificate, checkout the How to... section.

Added in v22.6


It should be noted that all of these have an equivalent in the Sanic CLI:

  --debug                        Run the server in debug mode
  -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
  -d, --dev                      debug + auto reload
  --auto-tls                     Create a temporary TLS certificate for local development (requires mkcert or trustme)
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