[FIXED] Django gives Bad Request (400) when DEBUG = False

Issue

I am new to django-1.6. When I run the django server with DEBUG = True, it's running perfectly. But when I change DEBUG to False in the settings file, then the server stopped and it gives the following error on the command prompt:

CommandError: You must set settings.ALLOWED_HOSTS if DEBUG is False.

After I changed ALLOWED_HOSTS to ["http://127.0.0.1:8000",], in the browser I get the error:

Bad Request (400)

Is it possible to run Django without debug mode?

Solution

The ALLOWED_HOSTS list should contain fully qualified host names, not urls. Leave out the port and the protocol. If you are using 127.0.0.1, I would add localhost to the list too:

ALLOWED_HOSTS = ['127.0.0.1', 'localhost']

You could also use * to match any host:

ALLOWED_HOSTS = ['*']

Quoting the documentation:

Values in this list can be fully qualified names (e.g. 'www.example.com'), in which case they will be matched against the request’s Host header exactly (case-insensitive, not including port). A value beginning with a period can be used as a subdomain wildcard: '.example.com' will match example.com, www.example.com, and any other subdomain of example.com. A value of '*' will match anything; in this case you are responsible to provide your own validation of the Host header (perhaps in a middleware; if so this middleware must be listed first in MIDDLEWARE_CLASSES).

Bold emphasis mine.

The status 400 response you get is due to a SuspiciousOperation exception being raised when your host header doesn't match any values in that list.

Answered By - Martijn Pieters