Buckets & Objects

Buckets and objects are the two fundamental resources in Cloud Storage. A bucket is a container that holds objects, and an object is an immutable blob of data (a file) with associated metadata. Understanding how to create, configure, and manage buckets and objects is essential for effective use of Cloud Storage.

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Buckets

A bucket is a top-level container for objects. Every object must reside in a bucket.

Bucket Naming Rules

• Globally unique across all of GCP (not just your project)
• 3 to 63 characters, lowercase letters, numbers, hyphens, and underscores
• Must start and end with a letter or number
• Cannot contain "goog" or misspellings of "google"
• Cannot be an IP address format

Bucket Location Types

Location Type	Example	Description
Region	europe-west2	Single data centre location — lowest latency, lowest cost
Dual-region	eur4 (Finland + Netherlands)	Two specific regions — higher availability
Multi-region	EU, US, ASIA	Multiple data centres across a large geographic area — highest availability

The location is set at bucket creation time and cannot be changed afterwards.

Creating Buckets

# Create a regional bucket
gsutil mb -l europe-west2 -c standard gs://my-regional-bucket

# Create a multi-region bucket
gsutil mb -l EU -c standard gs://my-eu-bucket

# Create a dual-region bucket
gsutil mb -l eur4 -c nearline gs://my-dual-region-bucket

# Using gcloud storage
gcloud storage buckets create gs://my-bucket \
  --location=europe-west2 \
  --default-storage-class=standard \
  --uniform-bucket-level-access

Bucket Configuration

Setting	Description
Default storage class	Applied to new objects unless overridden
Uniform bucket-level access	Uses IAM only (recommended); disables ACLs
Public access prevention	Blocks allUsers/allAuthenticatedUsers grants
Versioning	Preserves non-current versions of overwritten/deleted objects
Retention policy	Prevents deletion until a minimum retention period expires
Labels	Key-value pairs for cost tracking and organisation
Autoclass	Automatically transitions objects between storage classes

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Objects

Objects are the individual data items stored in buckets. Each object consists of:

Object Components

Component	Description
Object data	The file content (binary or text)
Object name (key)	The unique identifier within the bucket (e.g., images/photo.jpg)
Generation number	A unique version ID that changes each time the object is overwritten
Metageneration	Tracks metadata-only changes
Metadata	System and custom key-value pairs

Object Names and Simulated Directories

Cloud Storage has a flat namespace — there are no real directories. Forward slashes in object names simulate a directory structure: