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Controlling who can read a bucket, and what uniform access changes

Cloud Storage supports two access control systems: uniform bucket-level access, which relies solely on Cloud IAM policies applied consistently to all objects in a bucket, and fine-grained access, which combines IAM with legacy Access Control Lists (ACLs) that can be set per object or bucket. Choosing the right method affects how you manage public exposure, permission granularity, and compliance requirements for your data.

Must-know

  • Uniform bucket-level access disables ACLs entirely, enforcing IAM permissions uniformly across all objects in the bucket, which simplifies auditing and is Google's recommended default for most workloads.
  • Fine-grained access allows individual objects to have different permissions via ACLs (e.g., one object public, another private) even within the same bucket, but adds management complexity.
  • Public access can be granted by assigning the allUsers or allAuthenticatedUsers identity IAM role (like Storage Object Viewer) at the bucket or object level, making data readable without authentication.
  • Public Access Prevention (PAP) is an organization policy/bucket setting that blocks public access regardless of IAM or ACL grants, providing an extra safeguard against accidental exposure.
  • Once uniform bucket-level access is enabled, it can be reverted to fine-grained only within 90 days; after that window the switch becomes permanent for that bucket.
  • Signed URLs and signed policy documents offer a time-limited, credential-free way to grant temporary access to specific objects without changing bucket-level IAM or ACL settings.
Check this objectiveFree · always available

A data practitioner manages a Cloud Storage bucket that stores analytics exports for several teams. The security team wants all access to the bucket to be governed exclusively through IAM policies, with no possibility of individual objects having different permissions set through access control lists (ACLs). Which setting should the practitioner configure on the bucket?

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Coverage checked against the published exam guide on Aug 12, 2026.

These are independent practice questions, written against this certification's published exam guide. They are not the certification vendor's own questions, and not the real exam.