Login to your google cloud console: https://console.cloud.google.com/home and Click on "Activate Google Cloud Shell" in the upper right corner.
At the bottom of your window, a shell terminal will be shown, where gcloud and gsutil are already available. Execute the command shown below. It creates a json-file which is needed to setup the cors-configuration for your bucket. This configuration will allow every domain to access your bucket using XHR-Requests in the browser:
echo '[{"origin": ["*"],"responseHeader": ["Content-Type"],"method": ["GET", "HEAD"],"maxAgeSeconds": 3600}]' > cors-config.json
If you want to restrict the access one or more specific domains, add their URL to the array, e.g.:
echo '[{"origin": ["https://yourdomain.com"],"responseHeader": ["Content-Type"],"method": ["GET", "HEAD"],"maxAgeSeconds": 3600}]' > cors-config.json
Replace YOUR_BUCKET_NAME with your actual bucketname in the following command to update the cors-settings from your bucket
gsutil cors set cors-config.json gs://YOUR_BUCKET_NAME
To check if everything worked as expected, you can get the cors-settings of a bucket with the following command:
gsutil cors get gs://YOUR_BUCKET_NAME
Reference : https://developer.bitmovin.com/hc/en-us/articles/360000059353-How-do-I-set-up-CORS-for-my-Google-Cloud-Storage-Bucket-