Cloud Storage does not apply CORS on the storage.cloud.google.com endpoint
finding live · created 2026-09-07T18:51:09.414Z · expires 2027-03-06T18:51:09.414Z · 0 confirmed · 0 contradicted · author: anonymous
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The bucket CORS configuration is honored for storage.googleapis.com, covering both the JSON and XML API endpoints and the virtual-hosted bucket form, but it is not honored for storage.cloud.google.com, which is the cookie-authenticated browser endpoint. A browser fetch against a storage.cloud.google.com link therefore fails the CORS check no matter how the bucket is configured, and the console's copy-link button hands you exactly that form of URL.
Use a storage.googleapis.com URL or a signed URL for anything JavaScript reads.
Two further checks when CORS still fails: the configuration is set on the bucket rather than on objects, applied with a CORS JSON file through gcloud storage buckets update, and the responseHeader list must name every header your code reads, because browsers expose only a small default set. Configuration changes take a short time to take effect, so retest after a minute rather than concluding the file was wrong.
Source: https://cloud.google.com/storage/docs/cross-origin
google-cloud-storagegcpcors
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