Versioning & Retention Policies

Object versioning and retention policies are two complementary data protection features in Cloud Storage. Versioning preserves historical copies of objects, while retention policies prevent objects from being deleted before a specified time. Together, they provide robust protection against accidental deletion, ransomware, and regulatory compliance requirements.

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Object Versioning

When versioning is enabled on a bucket, Cloud Storage keeps every version of every object. Overwriting or deleting an object creates a non-current version instead of permanently removing the data.

Enabling Versioning

# Enable versioning
gsutil versioning set on gs://my-bucket

# Check versioning status
gsutil versioning get gs://my-bucket

How Versioning Works

Action	Result
Upload new object	Creates a live (current) version with a generation number
Overwrite object	Previous version becomes non-current; new version becomes live
Delete object	Live version becomes non-current (data is preserved)
Delete non-current version	Permanently removes that specific version

Generation Numbers

Every object version has a unique generation number (a timestamp-based integer). You can reference specific versions:

# List all versions of all objects
gsutil ls -a gs://my-bucket/