Learn how to deal with CORS Error Docker Flask Container. Our Docker Support team is here to help you with your questions and concerns.

CORS Error Docker Flask Container | Fixed

If you have been coming across CORS issues, you have come to the right place. One of our customers recently ran into CORS issues when their frontend application running in a browser tried to access a server running in a Docker container.

If you are facing similar CORS issues on local development with Docker, take a look at these steps:

• First, we can try configuring the server to include the corresponding CORS headers in its responses. This includes adding headers like Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers to the server’s responses.
• Next, we can set up a reverse proxy server between the frontend application and the API server running in Docker. Then, the API server does not have to handle CORS directly.
• Then, if we use a frontend development server like webpack-dev-server, we can configure it to proxy requests to the API server running in Docker.
• Next, we must disable CORS restrictions with browser extensions or start the browser with security features disabled. However, this is recommended only for local development.

How to resolve the CORS error in your Docker Flask container

1. First, we have to install the Flask-CORS extension to handle CORS-related headers.
2. Then, we must import the flask_cors module and initialize CORS by wrapping our Flask app instance with it. For instance:

   from flask import Flask
from flask_cors import CORS
app = Flask(__name__)
cors = CORS(app)

3. Next, we have to configure CORS options to specify the allowed origins, methods, headers, and other settings.
4. Now it is time to restart the Docker container to apply the modifications. Remember to make sure that the Flask app inside the container is now using the Flask-CORS extension.

After the above steps, the Flask application running within the Docker container will be able to handle CORS requests properly.

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Conclusion

To conclude, our Support Techs demonstrated how to resolve CORS Error in Docker Flask Container.