Bucket metadata

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This page discusses the metadata fields that are stored along with buckets in Cloud Storage.

Introduction

Cloud Storage buckets have metadata associated with them. Metadata identifies properties of the bucket and specifies how the bucket should be handled when it's accessed.

Metadata is stored as key: value pairs, where the value can take a variety of forms, including strings, arrays, or even nested key:value pairs. For example, the bucket name is a string, while a bucket Object Lifecycle Management configuration is an array of rules in which each rule contains several child key: value pairs.

The mutability of metadata varies:

• Some you can only view.

• Some you can only set when the bucket is first created, and cannot edit or remove.

• Some you can add and edit, but not remove.

• Some you can add, edit, and remove at any time.

Non-editable metadata

The following metadata is set during bucket creation, and cannot be edited or removed:

• Bucket name

• The project the bucket is a part of

• Generation number

  • A bucket's generation number uniquely identifies the version of the bucket even if more than one version of a bucket share the same name.

  • A bucket's generation value never changes.

  • There is no guarantee that generation numbers increase for successive versions, only that each new version has a unique generation number.

  • There is no relationship between generation numbers of unrelated buckets.

• Metageneration number

  • A bucket's metageneration number uniquely identifies the metadata state of the bucket. The metageneration number is 1 at the time of bucket creation and increases each time you modify the bucket's metadata.

Editable metadata

Editable bucket metadata is metadata whose values you can typically modify at any time. In some cases, such as the bucket being subject to an organization policy constraint, there are restrictions on modifying certain metadata values.

Metadata overview	Link to guide	Notes
Access Control Lists (ACLs)	Create and managing ACLs	Recommended only for XML users.
Default ACLs	Set default object ACLs
Identity and Access Management (IAM) policies1	Use IAM permissions
Billing (Requester Pays)	Use Requester Pays
Cross-origin resource sharing (CORS) configuration	Set up and view CORS configurations
Default storage class	Change the default storage class	Set during bucket creation and can be edited, but not removed.
Default Cloud KMS encryption key	Use default Cloud KMS keys
Default event-based holds1	Work with the default event-based hold property
Public access prevention1	Use public access prevention
Uniform bucket-level access1	Use uniform bucket-level access	Only editable for the first 90 days after you enable uniform bucket-level access on a bucket.
Lifecycle configuration policy	Manage object lifecycles
Autoclass	Use Autoclass
Turbo replication1	Manage turbo replication
Usage logs and storage logs	Usage logs configuration
Bucket Lock2	Use and locking retention policies	Only editable if you don't lock the retention policy.
Object Retention Lock	Enable and use object retention configurations	Once enabled for a bucket, cannot be disabled.
Object Versioning configuration	Use Object Versioning
Bucket labels	Use bucket labels
Soft delete retention duration	Use soft delete
Website configuration	Assign specialty pages for static websites
Bucket location	Relocate buckets	Before you relocate a bucket, review the Bucket relocation overview page.

¹ This metadata cannot be viewed or managed using the XML API.

² You can use the XML API to set this metadata during bucket creation, but not to view or manage this metadata.

What's next

• Learn how to view bucket metadata.
• Read more about object metadata.