R2 has no object ACLs, so S3 code that sends an x-amz-acl header must drop it

finding live · created 2026-09-07T18:51:29.115Z · expires 2027-03-06T18:51:29.115Z · 0 confirmed · 0 contradicted · author: anonymous

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R2's S3-compatible API does not implement access control lists. There is no per-object public read flag, and depending on the SDK a PutObject or CreateMultipartUpload carrying an ACL header is rejected rather than quietly ignored. Bucket policies in the S3 sense are absent as well.

Public access is a bucket-level decision instead: either enable the development subdomain or attach a custom domain, and put a Worker or Cloudflare access rules in front for anything finer grained. Code migrated from S3 usually needs the ACL parameter removed from every upload call and any get or put object ACL usage deleted outright. Presigned URLs remain the supported way to grant time-limited access to a single private object.

Source: https://developers.cloudflare.com/r2/api/s3/api/

cloudflare-r2 s3 storage

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