A Django App that adds Cross-Origin Resource Sharing (CORS) headers to responses. This allows in-browser requests to your Django application from other origins.
Adding CORS headers allows your resources to be accessed on other domains. It's important you understand the implications before adding the headers, since you could be unintentionally opening up your site's private data to others.
Some good resources to read on the subject are:
- Julia Evans' introductory comic and educational quiz.
- Jake Archibald’s How to win at CORS
- The MDN Article
- The HTML5 Rocks Tutorial
- The Wikipedia Page
Python 3.6 to 3.10 supported.
Django 2.2 to 4.0 supported.
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Install from pip:
python -m pip install django-cors-headersand then add it to your installed apps:
INSTALLED_APPS = [
...,
"corsheaders",
...,
]Make sure you add the trailing comma or you might get a ModuleNotFoundError
(see this blog
post).
You will also need to add a middleware class to listen in on responses:
MIDDLEWARE = [
...,
"corsheaders.middleware.CorsMiddleware",
"django.middleware.common.CommonMiddleware",
...,
]CorsMiddleware should be placed as high as possible, especially before any
middleware that can generate responses such as Django's CommonMiddleware or
Whitenoise's WhiteNoiseMiddleware. If it is not before, it will not be able
to add the CORS headers to these responses.
Also if you are using CORS_REPLACE_HTTPS_REFERER it should be placed before
Django's CsrfViewMiddleware (see more below).
django-cors-headers was created in January 2013 by Otto Yiu. It went unmaintained from August 2015 and was forked in January 2016 to the package django-cors-middleware by Laville Augustin at Zeste de Savoir. In September 2016, Adam Johnson, Ed Morley, and others gained maintenance responsibility for django-cors-headers (Issue 110) from Otto Yiu. Basically all of the changes in the forked django-cors-middleware were merged back, or re-implemented in a different way, so it should be possible to switch back. If there's a feature that hasn't been merged, please open an issue about it.
django-cors-headers has had 40+ contributors in its time; thanks to every one of them.
Configure the middleware's behaviour in your Django settings. You must set at least one of three following settings:
CORS_ALLOWED_ORIGINSCORS_ALLOWED_ORIGIN_REGEXESCORS_ALLOW_ALL_ORIGINS
A list of origins that are authorized to make cross-site HTTP requests.
Defaults to [].
An Origin is defined by the CORS RFC Section 3.2 as a URI scheme + hostname + port, or one of the special values 'null' or 'file://'. Default ports (HTTPS = 443, HTTP = 80) are optional here.
The special value null is sent by the browser in
"privacy-sensitive contexts",
such as when the client is running from a file:// domain.
The special value file:// is sent accidentally by some versions of Chrome on
Android as per this bug.
Example:
CORS_ALLOWED_ORIGINS = [
"https://example.com",
"https://sub.example.com",
"http://localhost:8080",
"http://127.0.0.1:9000",
]Previously this setting was called CORS_ORIGIN_WHITELIST, which still works
as an alias, with the new name taking precedence.
A list of strings representing regexes that match Origins that are authorized
to make cross-site HTTP requests. Defaults to []. Useful when
CORS_ALLOWED_ORIGINS is impractical, such as when you have a large number
of subdomains.
Example:
CORS_ALLOWED_ORIGIN_REGEXES = [
r"^https://\w+\.example\.com$",
]Previously this setting was called CORS_ORIGIN_REGEX_WHITELIST, which still
works as an alias, with the new name taking precedence.
If True, all origins will be allowed. Other settings restricting allowed
origins will be ignored. Defaults to False.
Setting this to True can be dangerous, as it allows any website to make
cross-origin requests to yours. Generally you'll want to restrict the list of
allowed origins with CORS_ALLOWED_ORIGINS or
CORS_ALLOWED_ORIGIN_REGEXES.
Previously this setting was called CORS_ORIGIN_ALLOW_ALL, which still
works as an alias, with the new name taking precedence.
The following are optional settings, for which the defaults probably suffice.
A regex which restricts the URL's for which the CORS headers will be sent.
Defaults to r'^.*$', 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 = list(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 = list(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
CORS MDN article.
If True, cookies will be allowed to be included in cross-site HTTP
requests. Defaults to False.
Note: in Django 2.1 the SESSION_COOKIE_SAMESITE setting was added, set to
'Lax' by default, which will prevent Django's session cookie being sent
cross-domain. Change it to None to bypass this security restriction.
Most sites will need to take advantage of the Cross-Site Request Forgery
protection that Django
offers. CORS and CSRF are separate, and Django has no way of using your CORS
configuration to exempt sites from the Referer checking that it does on
secure requests. The way to do that is with its CSRF_TRUSTED_ORIGINS setting.
For example:
CORS_ALLOWED_ORIGINS = [
"http://read.only.com",
"http://change.allowed.com",
]
CSRF_TRUSTED_ORIGINS = [
"change.allowed.com",
]CSRF_TRUSTED_ORIGINS was introduced in Django 1.9, so users of earlier
versions will need an alternate solution. If CORS_REPLACE_HTTPS_REFERER is
True, CorsMiddleware will change the Referer header to something
that will pass Django's CSRF checks whenever the CORS checks pass. Defaults to
False.
Note that unlike CSRF_TRUSTED_ORIGINS, this setting does not allow you to
distinguish between domains that are trusted to read resources by CORS and
domains that are trusted to change resources by avoiding CSRF protection.
With this feature enabled you should also add
corsheaders.middleware.CorsPostCsrfMiddleware after
django.middleware.csrf.CsrfViewMiddleware in your MIDDLEWARE_CLASSES to
undo the Referer replacement:
MIDDLEWARE_CLASSES = [
...,
"corsheaders.middleware.CorsMiddleware",
...,
"django.middleware.csrf.CsrfViewMiddleware",
"corsheaders.middleware.CorsPostCsrfMiddleware",
...,
]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 myapp.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 myapp import handlers # noqaA 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_ALLOWED_ORIGINS 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)