How to Configure CORS in Firebase Storage

When you deploy your web app to a custom domain, the domain and the Firebase Storage bucket are hosted on different servers. This means that the browser will block requests to the Firebase Storage bucket from your web app, because the origins (the domains and ports) of the two servers are different.

What is CORS?

CORS stands for Cross-Origin Resource Sharing. It allows you to specify which origins are allowed to access your resources. By configuring CORS, you can tell the browser that your web app is allowed to make requests to the Firebase Storage bucket, even though the two servers are hosted on different domains.

How to configure CORS in Firebase Storage

In Firebase Storage, you can configure CORS by creating a cors.json file in your bucket. This file contains a list of origins that are allowed to access your resources.

To create a cors.json file, follow these steps:

Go to the Google Cloud Console: https://console.cloud.google.com
In the top right corner of the console, click the Activate Cloud Shell button.
you will see a terminal window inside your current window
Run the following command:

gcloud config set project <your-project-id>

Navigate to your Firebase Storage bucket:

cd gs://<your-bucket-name>

Run the cors command to configure CORS:

gsutil cors set cors.json gs://<your-bucket-name>

You can also specify a list of allowed headers by running the following command:

gsutil cors set cors.json gs://<your-bucket-name> --allowed-headers="Content-Type, Authorization"

The cors.json file contains a list of origins that are allowed to access your resources. Each origin is a string that identifies a domain or port. For example, the following origin allows access from the domain www.example.com:

"origins": ["https://www.example.com"]

You can also specify a list of allowed headers. The following example allows access to the Content-Type and Authorization headers:

"origins": ["https://www.example.com"], "allowedHeaders": ["Content-Type", "Authorization"]

For more information on configuring CORS in Firebase Storage, please see the official documentation

Conclusion

Configuring CORS in Firebase Storage can be a bit daunting, but it is a necessary step if you want to allow access to your resources from a different origin. By following the steps in this article, you can easily configure CORS and ensure that your resources are accessible to the right people.