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A Flask extension adding a decorator for CORS support

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A Flask extension for handling Cross Origin Resource Sharing (CORS), making cross-origin AJAX possible.


Install the extension with using pip, or easy_install.

$ pip install flask-cors


This extension enables CORS support either via a decorator, or a Flask extension. There are three examples shown in the examples directory, showing the major use cases. The suggested configuration is the, or the

Simple Usage

In the simplest case, initialize the Flask-Cors extension with default arguments in order to allow CORS on all routes.

app = Flask(__name__)
cors = CORS(app)

def helloWorld():
  return "Hello, cross-origin-world!"

Resource specific CORS

Alternatively, a list of resources and associated settings for CORS can be supplied, selectively enables CORS support on a set of paths on your app.

Note: this resources parameter can also be set in your application’s config.

app = Flask(__name__)
cors = CORS(app, resources={r"/api/*": {"origins": "*"}})

def list_users():
  return "user example"

Route specific CORS via decorator

This extension also exposes a simple decorator to decorate flask routes with. Simply add @cross_origin() below a call to Flask’s @app.route(..) incanation to accept the default options and allow CORS on a given route.

@cross_origin() # allow all origins all methods.
def helloWorld():
  return "Hello, cross-origin-world!"

Using JSON with CORS

When using JSON cross origin, browsers will issue a pre-flight OPTIONS request for POST requests. In order for browsers to allow POST requests with a JSON content type, you must allow the Content-Type header. The simplest way to do this is to simply set the CORS_HEADERS configuration value on your application, e.g:

app.config['CORS_HEADERS'] = 'Content-Type'

Application-wide settings

Alternatively, you can set all parameters except automatic_options in an app’s config object. Setting these at the application level effectively changes the default value for your application, while still allowing you to override it on a per-resource basis, either via the CORS Flask-Extension and regular expressions, or via the @cross_origin() decorator.

The application-wide configuration options are identical to the keyword arguments to cross_origin, creatively prefixed with CORS_










For a full list of options, please see the full documentation


A simple set of tests is included in test/. To run, install nose, and simply invoke nosetests or python test to exercise the tests.


Questions, comments or improvements? Please create an issue on Github, tweet at @wcdolphin or send me an email.


This Flask extension is based upon the Decorator for the HTTP Access Control written by Armin Ronacher.

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