A Django App that adds CORS (Cross-Origin Resource Sharing) headers to responses.

Although JSON-P is useful, it is strictly limited to GET requests. CORS builds on top of XmlHttpRequest to allow developers to make cross-domain requests, similar to same-domain requests. Read more about it here: http://www.html5rocks.com/en/tutorials/cors/

Tested with all combinations of:

• Python: 2.7, 3.5
• Django: 1.8, 1.9, 1.10

Install from pip:

pip install django-cors-headers

and then add it to your installed apps:

INSTALLED_APPS = (
    ...
    'corsheaders',
    ...
)

You will also need to add a middleware class to listen in on responses:

MIDDLEWARE_CLASSES = [
    ...
    'corsheaders.middleware.CorsMiddleware',
    'django.middleware.common.CommonMiddleware',
    ...
]

Note that CorsMiddleware needs to come before Django's CommonMiddleware if you are using Django's USE_ETAGS = True setting, otherwise the CORS headers will be lost from 304 Not-Modified responses, causing errors in some browsers.

Configure the middleware's behaviour in your Django settings. You must add the hosts that are allowed to do cross-site requests to CORS_ORIGIN_WHITELIST, or set CORS_ORIGIN_ALLOW_ALL to True to allow all hosts.

If True, the whitelist will not be used and all origins will be accepted. Defaults to False.

A list of origin hostnames that are authorized to make cross-site HTTP requests. Defaults to [].

Example:

CORS_ORIGIN_WHITELIST = (
    'google.com',
    'hostname.example.com',
    'localhost:8000',
    '127.0.0.1:9000'
)

A list of regexes that match origin regex list of origin hostnames that are authorized to make cross-site HTTP requests. Defaults to []. Useful when CORS_ORIGIN_WHITELIST is impractical, such as when you have a large number of subdomains.

Example:

CORS_ORIGIN_REGEX_WHITELIST = ('^(https?://)?(\w+\.)?google\.com$', )

The following are optional settings, for which the defaults probably suffice.

A regex which restricts the URL's for which the CORS headers will be sent. Defaults to r'^.*$', i.e. match all URL's. Useful when you only need CORS on a part of your site, e.g. an API at /api/.

Example:

CORS_URLS_REGEX = r'^/api/.*$'

A list of HTTP verbs that are allowed for the actual request. Defaults to:

CORS_ALLOW_METHODS = (
    'DELETE',
    'GET',
    'OPTIONS',
    'PATCH',
    'POST',
    'PUT',
)

The default can be imported as corsheaders.defaults.default_methods so you can just extend it with your custom methods. This allows you to keep up to date with any future changes. For example:

from corsheaders.defaults import default_methods

CORS_ALLOW_METHODS = default_methods + (
    'POKE',
)

The list of non-standard HTTP headers that can be used when making the actual request. Defaults to:

CORS_ALLOW_HEADERS = (
    'accept',
    'accept-encoding',
    'authorization',
    'content-type',
    'dnt',
    'origin',
    'user-agent',
    'x-csrftoken',
    'x-requested-with',
)

The default can be imported as corsheaders.defaults.default_headers so you can extend it with your custom headers. This allows you to keep up to date with any future changes. For example:

from corsheaders.defaults import default_headers

CORS_ALLOW_HEADERS = default_headers + (
    'my-custom-header',
)

The list of HTTP headers that are to be exposed to the browser. Defaults to [].

The number of seconds a client/browser can cache the preflight response. If this is 0 (or any falsey value), no max age header will be sent. Defaults to 86400 (one day).

Note: A preflight request is an extra request that is made when making a "not-so-simple" request (e.g. Content-Type is not application/x-www-form-urlencoded) to determine what requests the server actually accepts. Read more about it in the HTML 5 Rocks CORS tutorial.

If True, cookies will be allowed to be included in cross-site HTTP requests. Defaults to False.

If True, the HTTP_REFERER header will get replaced when CORS checks pass, so that the Django CSRF middleware checks work with HTTPS. Defaults to False.

Note: With this feature enabled, you also need to add corsheaders.middleware.CorsPostCsrfMiddleware after django.middleware.csrf.CsrfViewMiddleware in your MIDDLEWARE_CLASSES to undo the header replacement.

If set, this should be the path to a model to look up allowed origins, in the form app.modelname. Defaults to None.

The model should have one field, a CharField called cors, that in each instance contains an allowed origin. django-cors-headers supplies such a model for you; set the setting to corsheaders.CorsModel to use it.

If you have a use case that requires more than just the above configuration, you can attach code to check if a given request should be allowed. For example, this can be used to read the list of origins you allow from a model. Attach any number of handlers to the check_request_enabled Django signal, which provides the request argument (use **kwargs in your handler to protect against any future arguments being added). If any handler attached to the signal returns a truthy value, the request will be allowed.

For example you might define a handler like this:

# myapp/handlers.py
from corsheaders.signals import check_request_enabled

from .models import MySite

def cors_allow_mysites(sender, request, **kwargs):
    return MySite.objects.filter(host=request.host).exists()

check_request_enabled.connect(cors_allow_mysites)

Then connect it at app ready time using a Django AppConfig:

# myapp/__init__.py

default_app_config = 'myapp.apps.MyAppConfig'

# myapp/apps.py

from django.apps import AppConfig

class MyAppConfig(AppConfig):
    name = 'myapp'

    def ready(self):
        # Makes sure all signal handlers are connected
        from . import handlers  # noqa

A common use case for the signal is to allow all origins to access a subset of URL's, whilst allowing a normal set of origins to access all URL's. This isn't possible using just the normal configuration, but it can be achieved with a signal handler.

First set CORS_ORIGIN_WHITELIST to the list of trusted origins that are allowed to access every URL, and then add a handler to check_request_enabled to allow CORS regardless of the origin for the unrestricted URL's. For example:

# myapp/handlers.py
from corsheaders.signals import check_request_enabled

def cors_allow_api_to_everyone(sender, request, **kwargs):
    return request.path.startswith('/api/')

check_request_enabled.connect(cors_allow_api_to_everyone)

django-cors-headers was created by Otto Yiu (@ottoyiu) and has been worked on by 25+ contributors. Thanks to every contributor, and if you want to get involved please don't hesitate to make a pull request.