Set up and view CORS configurations

Go to concepts

Cross Origin Resource Sharing (CORS) allows interactions between resources from different origins, something that is normally prohibited in order to prevent malicious behavior. Use this topic to learn how to set a CORS configuration on a Cloud Storage bucket and how to view the CORS configuration set on a bucket. See Configuration examples for CORS for example CORS configurations, including the configuration that disables any existing configuration on your bucket.

Set the CORS configuration on a bucket

You set a CORS configuration on a bucket by specifying information, such as HTTP methods and originating domains, that identify the types of requests the bucket can accept.

Use the following steps to set a CORS configuration on your bucket:

Console

You cannot manage CORS using the Google Cloud console. Use the gcloud CLI instead.

Command line

gcloud

1. Create a JSON file with the CORS configuration you would like to apply. See configuration examples for sample JSON files.

2. Use the gcloud storage buckets update command with the --cors-file flag:

   gcloud storage buckets update gs://BUCKET_NAME --cors-file=CORS_CONFIG_FILE

   Where:

   • BUCKET_NAME is the name of the relevant bucket. For example, my-bucket.
   • CORS_CONFIG_FILE is the path to the JSON file you created in Step 1.

gsutil

1. Create a JSON file with the CORS configuration you would like to apply. See configuration examples for sample JSON files.

2. Use the gsutil cors command to apply the configuration to a bucket:

   gsutil cors set CORS_CONFIG_FILE gs://BUCKET_NAME

   Where:

   • CORS_CONFIG_FILE is the path to the JSON file you created in Step 1.
   • BUCKET_NAME is the name of the relevant bucket. For example, my-bucket.

Client libraries

C++

For more information, see the Cloud Storage C++ API reference documentation.

The following sample sets a CORS configuration on a bucket:

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namespace gcs = ::google::cloud::storage;
using ::google::cloud::StatusOr;
[](gcs::Client client, std::string const& bucket_name,
   std::string const& origin) {
  StatusOr<gcs::BucketMetadata> original =
      client.GetBucketMetadata(bucket_name);

  if (!original) throw std::move(original).status();
  std::vector<gcs::CorsEntry> cors_configuration;
  cors_configuration.emplace_back(
      gcs::CorsEntry{3600, {"GET"}, {origin}, {"Content-Type"}});

  StatusOr<gcs::BucketMetadata> patched = client.PatchBucket(
      bucket_name,
      gcs::BucketMetadataPatchBuilder().SetCors(cors_configuration),
      gcs::IfMetagenerationMatch(original->metageneration()));
  if (!patched) throw std::move(patched).status();

  if (patched->cors().empty()) {
    std::cout << "Cors configuration is not set for bucket "
              << patched->name() << "\n";
    return;
  }

  std::cout << "Cors configuration successfully set for bucket "
            << patched->name() << "\nNew cors configuration: ";
  for (auto const& cors_entry : patched->cors()) {
    std::cout << "\n  " << cors_entry << "\n";
  }
}

C#

For more information, see the Cloud Storage C# API reference documentation.

The following sample sets a CORS configuration on a bucket:

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using Google.Apis.Storage.v1.Data;
using Google.Cloud.Storage.V1;
using System;
using System.Collections.Generic;
using static Google.Apis.Storage.v1.Data.Bucket;

public class BucketAddCorsConfigurationSample
{
    public Bucket BucketAddCorsConfiguration(string bucketName = "your-bucket-name")
    {
        var storage = StorageClient.Create();
        var bucket = storage.GetBucket(bucketName);

        CorsData corsData = new CorsData
        {
            Origin = new string[] { "*" },
            ResponseHeader = new string[] { "Content-Type", "x-goog-resumable" },
            Method = new string[] { "PUT", "POST" },
            MaxAgeSeconds = 3600 //One Hour
        };

        if (bucket.Cors == null)
        {
            bucket.Cors = new List<CorsData>();
        }
        bucket.Cors.Add(corsData);

        bucket = storage.UpdateBucket(bucket);
        Console.WriteLine($"bucketName {bucketName} was updated with a CORS config to allow {string.Join(",", corsData.Method)} requests from" +
            $" {string.Join(",", corsData.Origin)} sharing {string.Join(",", corsData.ResponseHeader)} responseHeader" +
            $" responses across origins.");
        return bucket;
    }
}

Go

For more information, see the Cloud Storage Go API reference documentation.

The following sample sets a CORS configuration on a bucket:

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import (
	"context"
	"fmt"
	"io"
	"time"

	"cloud.google.com/go/storage"
)

// setBucketCORSConfiguration sets a CORS configuration on a bucket.
func setBucketCORSConfiguration(w io.Writer, bucketName string, maxAge time.Duration, methods, origins, responseHeaders []string) error {
	// bucketName := "bucket-name"
	// maxAge := time.Hour
	// methods := []string{"GET"}
	// origins := []string{"some-origin.com"}
	// responseHeaders := []string{"Content-Type"}
	ctx := context.Background()
	client, err := storage.NewClient(ctx)
	if err != nil {
		return fmt.Errorf("storage.NewClient: %v", err)
	}
	defer client.Close()

	ctx, cancel := context.WithTimeout(ctx, time.Second*10)
	defer cancel()

	bucket := client.Bucket(bucketName)
	bucketAttrsToUpdate := storage.BucketAttrsToUpdate{
		CORS: []storage.CORS{
			{
				MaxAge:          maxAge,
				Methods:         methods,
				Origins:         origins,
				ResponseHeaders: responseHeaders,
			}},
	}
	if _, err := bucket.Update(ctx, bucketAttrsToUpdate); err != nil {
		return fmt.Errorf("Bucket(%q).Update: %v", bucketName, err)
	}
	fmt.Fprintf(w, "Bucket %v was updated with a CORS config to allow %v requests from %v sharing %v responses across origins\n", bucketName, methods, origins, responseHeaders)
	return nil
}

Java

For more information, see the Cloud Storage Java API reference documentation.

The following sample sets a CORS configuration on a bucket:

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import com.google.cloud.storage.Bucket;
import com.google.cloud.storage.Cors;
import com.google.cloud.storage.HttpMethod;
import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;
import com.google.common.collect.ImmutableList;

public class ConfigureBucketCors {
  public static void configureBucketCors(
      String projectId,
      String bucketName,
      String origin,
      String responseHeader,
      Integer maxAgeSeconds) {
    // The ID of your GCP project
    // String projectId = "your-project-id";

    // The ID of your GCS bucket
    // String bucketName = "your-unique-bucket-name";

    // The origin for this CORS config to allow requests from
    // String origin = "http://example.appspot.com";

    // The response header to share across origins
    // String responseHeader = "Content-Type";

    // The maximum amount of time the browser can make requests before it must repeat preflighted
    // requests
    // Integer maxAgeSeconds = 3600;

    Storage storage = StorageOptions.newBuilder().setProjectId(projectId).build().getService();
    Bucket bucket = storage.get(bucketName);

    // See the HttpMethod documentation for other HTTP methods available:
    // https://cloud.google.com/appengine/docs/standard/java/javadoc/com/google/appengine/api/urlfetch/HTTPMethod
    HttpMethod method = HttpMethod.GET;

    Cors cors =
        Cors.newBuilder()
            .setOrigins(ImmutableList.of(Cors.Origin.of(origin)))
            .setMethods(ImmutableList.of(method))
            .setResponseHeaders(ImmutableList.of(responseHeader))
            .setMaxAgeSeconds(maxAgeSeconds)
            .build();

    bucket.toBuilder().setCors(ImmutableList.of(cors)).build().update();

    System.out.println(
        "Bucket "
            + bucketName
            + " was updated with a CORS config to allow GET requests from "
            + origin
            + " sharing "
            + responseHeader
            + " responses across origins");
  }
}

Node.js

For more information, see the Cloud Storage Node.js API reference documentation.

The following sample sets a CORS configuration on a bucket:

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// Imports the Google Cloud client library
const {Storage} = require('@google-cloud/storage');

// Creates a client
const storage = new Storage();

/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
// The ID of your GCS bucket
// const bucketName = 'your-unique-bucket-name';

// The origin for this CORS config to allow requests from
// const origin = 'http://example.appspot.com';

// The response header to share across origins
// const responseHeader = 'Content-Type';

// The maximum amount of time the browser can make requests before it must
// repeat preflighted requests
// const maxAgeSeconds = 3600;

// The name of the method
// See the HttpMethod documentation for other HTTP methods available:
// https://cloud.google.com/appengine/docs/standard/java/javadoc/com/google/appengine/api/urlfetch/HTTPMethod
// const method = 'GET';

async function configureBucketCors() {
  await storage.bucket(bucketName).setCorsConfiguration([
    {
      maxAgeSeconds,
      method: [method],
      origin: [origin],
      responseHeader: [responseHeader],
    },
  ]);

  console.log(`Bucket ${bucketName} was updated with a CORS config
      to allow ${method} requests from ${origin} sharing 
      ${responseHeader} responses across origins`);
}

configureBucketCors().catch(console.error);

PHP

For more information, see the Cloud Storage PHP API reference documentation.

The following sample sets a CORS configuration on a bucket:

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use Google\Cloud\Storage\StorageClient;

/**
 * Update the CORS configuration of a bucket.
 *
 * @param string $bucketName The name of your Cloud Storage bucket.
 *        (e.g. 'my-bucket')
 * @param string $method The HTTP method for the CORS config. (e.g. 'GET')
 * @param string $origin The origin from which the CORS config will allow requests.
 *        (e.g. 'http://example.appspot.com')
 * @param string $responseHeader The response header to share across origins.
 *        (e.g. 'Content-Type')
 * @param int $maxAgeSeconds The maximum amount of time the browser can make
 *        (e.g. 3600)
 *     requests before it must repeat preflighted requests.
 */
function cors_configuration(string $bucketName, string $method, string $origin, string $responseHeader, int $maxAgeSeconds): void
{
    $storage = new StorageClient();
    $bucket = $storage->bucket($bucketName);

    $bucket->update([
        'cors' => [
            [
                'method' => [$method],
                'origin' => [$origin],
                'responseHeader' => [$responseHeader],
                'maxAgeSeconds' => $maxAgeSeconds,
            ]
        ]
    ]);

    printf(
        'Bucket %s was updated with a CORS config to allow GET requests from ' .
        '%s sharing %s responses across origins.',
        $bucketName,
        $origin,
        $responseHeader
    );
}

Python

For more information, see the Cloud Storage Python API reference documentation.

The following sample sets a CORS configuration on a bucket:

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from google.cloud import storage


def cors_configuration(bucket_name):
    """Set a bucket's CORS policies configuration."""
    # bucket_name = "your-bucket-name"

    storage_client = storage.Client()
    bucket = storage_client.get_bucket(bucket_name)
    bucket.cors = [
        {
            "origin": ["*"],
            "responseHeader": [
                "Content-Type",
                "x-goog-resumable"],
            "method": ['PUT', 'POST'],
            "maxAgeSeconds": 3600
        }
    ]
    bucket.patch()

    print(f"Set CORS policies for bucket {bucket.name} is {bucket.cors}")
    return bucket

Ruby

For more information, see the Cloud Storage Ruby API reference documentation.

The following sample sets a CORS configuration on a bucket:

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def cors_configuration bucket_name:
  # The ID of your GCS bucket
  # bucket_name = "your-unique-bucket-name"

  require "google/cloud/storage"

  storage = Google::Cloud::Storage.new
  bucket = storage.bucket bucket_name

  bucket.cors do |c|
    c.add_rule ["*"],
               ["PUT", "POST"],
               headers: [
                 "Content-Type",
                 "x-goog-resumable"
               ],
               max_age: 3600
  end

  puts "Set CORS policies for bucket #{bucket_name}"
end

REST APIs

JSON API

1. Get an authorization access token from the OAuth 2.0 Playground. Configure the playground to use your own OAuth credentials. For instructions, see API authentication.

2. Create a JSON file with the CORS configuration you would like to apply. See configuration examples for sample JSON files.

3. Use cURL to call the JSON API with a PATCH Bucket request:

   curl --request PATCH \
    'https://storage.googleapis.com/storage/v1/b/BUCKET_NAME?fields=cors' \
    --header 'Authorization: Bearer OAUTH2_TOKEN' \
    --header 'Content-Type: application/json' \
    --data-binary @CORS_CONFIG_FILE

   Where:

   • BUCKET_NAME is the name of the bucket. For example, my-bucket.
   • OAUTH2_TOKEN is the access token you generated in Step 1.
   • CORS_CONFIG_FILE is the path to the JSON file you created in Step 2.

XML API

1. Get an authorization access token from the OAuth 2.0 Playground. Configure the playground to use your own OAuth credentials. For instructions, see API authentication.

2. Create a XML file with the CORS configuration you would like to apply. See configuration examples for sample XML files.

3. Use cURL to call the XML API with a Set Bucket CORS request:

   curl -X PUT --data-binary @CORS_CONFIG_FILE \
   -H "Authorization: Bearer OAUTH2_TOKEN" \
   -H "x-goog-project-id: PROJECT_ID" \
   "https://storage.googleapis.com/BUCKET_NAME?cors"

   Where:

   • BUCKET_NAME is the name of the bucket. For example, my-bucket.
   • OAUTH2_TOKEN is the access token you generated in Step 1.
   • PROJECT_ID is the ID of the project associated with the bucket. For example, my-project.
   • CORS_CONFIG_FILE is the path to the XML file you created in Step 2.

Note: To remove the CORS configuration for a bucket, set an empty CORS configuration.

View the CORS configuration for a bucket

To view the CORS configuration for a bucket:

Console

You cannot manage CORS using the Google Cloud console. Use the gcloud CLI instead.

Command line

gcloud

Use the gcloud storage buckets describe command with the --format flag:

gcloud storage buckets describe gs://BUCKET_NAME --format="default(cors)"

Where BUCKET_NAME is the name of the bucket whose CORS configuration you want to view. For example, my-bucket.

gsutil

Use the gsutil cors command to get the CORS configuration of a bucket:

gsutil cors get gs://BUCKET_NAME

Where BUCKET_NAME is the name of the bucket whose CORS configuration you want to view. For example, my-bucket.

Client libraries

To view the CORS configuration for a bucket using the client libraries, follow the instructions for displaying a bucket's metadata and look for the CORS field in the response:

C++

For more information, see the Cloud Storage C++ API reference documentation.

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namespace gcs = ::google::cloud::storage;
using ::google::cloud::StatusOr;
[](gcs::Client client, std::string const& bucket_name) {
  StatusOr<gcs::BucketMetadata> bucket_metadata =
      client.GetBucketMetadata(bucket_name);
  if (!bucket_metadata) throw std::move(bucket_metadata).status();

  std::cout << "The metadata for bucket " << bucket_metadata->name() << " is "
            << *bucket_metadata << "\n";
}

C#

For more information, see the Cloud Storage C# API reference documentation.

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using Google.Apis.Storage.v1.Data;
using Google.Cloud.Storage.V1;
using System;

public class GetBucketMetadataSample
{
    public Bucket GetBucketMetadata(string bucketName = "your-unique-bucket-name")
    {
        var storage = StorageClient.Create();
        var bucket = storage.GetBucket(bucketName, new GetBucketOptions { Projection = Projection.Full });
        Console.WriteLine($"Bucket:\t{bucket.Name}");
        Console.WriteLine($"Acl:\t{bucket.Acl}");
        Console.WriteLine($"Billing:\t{bucket.Billing}");
        Console.WriteLine($"Cors:\t{bucket.Cors}");
        Console.WriteLine($"DefaultEventBasedHold:\t{bucket.DefaultEventBasedHold}");
        Console.WriteLine($"DefaultObjectAcl:\t{bucket.DefaultObjectAcl}");
        Console.WriteLine($"Encryption:\t{bucket.Encryption}");
        if (bucket.Encryption != null)
        {
            Console.WriteLine($"KmsKeyName:\t{bucket.Encryption.DefaultKmsKeyName}");
        }
        Console.WriteLine($"Id:\t{bucket.Id}");
        Console.WriteLine($"Kind:\t{bucket.Kind}");
        Console.WriteLine($"Lifecycle:\t{bucket.Lifecycle}");
        Console.WriteLine($"Location:\t{bucket.Location}");
        Console.WriteLine($"LocationType:\t{bucket.LocationType}");
        Console.WriteLine($"Logging:\t{bucket.Logging}");
        Console.WriteLine($"Metageneration:\t{bucket.Metageneration}");
        Console.WriteLine($"Owner:\t{bucket.Owner}");
        Console.WriteLine($"ProjectNumber:\t{bucket.ProjectNumber}");
        Console.WriteLine($"RetentionPolicy:\t{bucket.RetentionPolicy}");
        Console.WriteLine($"SelfLink:\t{bucket.SelfLink}");
        Console.WriteLine($"StorageClass:\t{bucket.StorageClass}");
        Console.WriteLine($"TimeCreated:\t{bucket.TimeCreated}");
        Console.WriteLine($"Updated:\t{bucket.Updated}");
        Console.WriteLine($"Versioning:\t{bucket.Versioning}");
        Console.WriteLine($"Website:\t{bucket.Website}");
        Console.WriteLine($"TurboReplication:\t{bucket.Rpo}");
        if (bucket.Labels != null)
        {
            Console.WriteLine("Labels:");
            foreach (var label in bucket.Labels)
            {
                Console.WriteLine($"{label.Key}:\t{label.Value}");
            }
        }
        return bucket;
    }
}

Go

For more information, see the Cloud Storage Go API reference documentation.

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import (
	"context"
	"fmt"
	"io"
	"time"

	"cloud.google.com/go/storage"
)

// getBucketMetadata gets the bucket metadata.
func getBucketMetadata(w io.Writer, bucketName string) (*storage.BucketAttrs, error) {
	// bucketName := "bucket-name"
	ctx := context.Background()
	client, err := storage.NewClient(ctx)
	if err != nil {
		return nil, fmt.Errorf("storage.NewClient: %v", err)
	}
	defer client.Close()

	ctx, cancel := context.WithTimeout(ctx, time.Second*10)
	defer cancel()
	attrs, err := client.Bucket(bucketName).Attrs(ctx)
	if err != nil {
		return nil, fmt.Errorf("Bucket(%q).Attrs: %v", bucketName, err)
	}
	fmt.Fprintf(w, "BucketName: %v\n", attrs.Name)
	fmt.Fprintf(w, "Location: %v\n", attrs.Location)
	fmt.Fprintf(w, "LocationType: %v\n", attrs.LocationType)
	fmt.Fprintf(w, "StorageClass: %v\n", attrs.StorageClass)
	fmt.Fprintf(w, "Turbo replication (RPO): %v\n", attrs.RPO)
	fmt.Fprintf(w, "TimeCreated: %v\n", attrs.Created)
	fmt.Fprintf(w, "Metageneration: %v\n", attrs.MetaGeneration)
	fmt.Fprintf(w, "PredefinedACL: %v\n", attrs.PredefinedACL)
	if attrs.Encryption != nil {
		fmt.Fprintf(w, "DefaultKmsKeyName: %v\n", attrs.Encryption.DefaultKMSKeyName)
	}
	if attrs.Website != nil {
		fmt.Fprintf(w, "IndexPage: %v\n", attrs.Website.MainPageSuffix)
		fmt.Fprintf(w, "NotFoundPage: %v\n", attrs.Website.NotFoundPage)
	}
	fmt.Fprintf(w, "DefaultEventBasedHold: %v\n", attrs.DefaultEventBasedHold)
	if attrs.RetentionPolicy != nil {
		fmt.Fprintf(w, "RetentionEffectiveTime: %v\n", attrs.RetentionPolicy.EffectiveTime)
		fmt.Fprintf(w, "RetentionPeriod: %v\n", attrs.RetentionPolicy.RetentionPeriod)
		fmt.Fprintf(w, "RetentionPolicyIsLocked: %v\n", attrs.RetentionPolicy.IsLocked)
	}
	fmt.Fprintf(w, "RequesterPays: %v\n", attrs.RequesterPays)
	fmt.Fprintf(w, "VersioningEnabled: %v\n", attrs.VersioningEnabled)
	if attrs.Logging != nil {
		fmt.Fprintf(w, "LogBucket: %v\n", attrs.Logging.LogBucket)
		fmt.Fprintf(w, "LogObjectPrefix: %v\n", attrs.Logging.LogObjectPrefix)
	}
	if attrs.CORS != nil {
		fmt.Fprintln(w, "CORS:")
		for _, v := range attrs.CORS {
			fmt.Fprintf(w, "\tMaxAge: %v\n", v.MaxAge)
			fmt.Fprintf(w, "\tMethods: %v\n", v.Methods)
			fmt.Fprintf(w, "\tOrigins: %v\n", v.Origins)
			fmt.Fprintf(w, "\tResponseHeaders: %v\n", v.ResponseHeaders)
		}
	}
	if attrs.Labels != nil {
		fmt.Fprintf(w, "\n\n\nLabels:")
		for key, value := range attrs.Labels {
			fmt.Fprintf(w, "\t%v = %v\n", key, value)
		}
	}
	return attrs, nil
}

Java

For more information, see the Cloud Storage Java API reference documentation.

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import com.google.cloud.storage.Bucket;
import com.google.cloud.storage.BucketInfo;
import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;
import java.util.Map;

public class GetBucketMetadata {
  public static void getBucketMetadata(String projectId, String bucketName) {
    // The ID of your GCP project
    // String projectId = "your-project-id";

    // The ID of your GCS bucket
    // String bucketName = "your-unique-bucket-name";

    Storage storage = StorageOptions.newBuilder().setProjectId(projectId).build().getService();

    // Select all fields. Fields can be selected individually e.g. Storage.BucketField.NAME
    Bucket bucket =
        storage.get(bucketName, Storage.BucketGetOption.fields(Storage.BucketField.values()));

    // Print bucket metadata
    System.out.println("BucketName: " + bucket.getName());
    System.out.println("DefaultEventBasedHold: " + bucket.getDefaultEventBasedHold());
    System.out.println("DefaultKmsKeyName: " + bucket.getDefaultKmsKeyName());
    System.out.println("Id: " + bucket.getGeneratedId());
    System.out.println("IndexPage: " + bucket.getIndexPage());
    System.out.println("Location: " + bucket.getLocation());
    System.out.println("LocationType: " + bucket.getLocationType());
    System.out.println("Metageneration: " + bucket.getMetageneration());
    System.out.println("NotFoundPage: " + bucket.getNotFoundPage());
    System.out.println("RetentionEffectiveTime: " + bucket.getRetentionEffectiveTime());
    System.out.println("RetentionPeriod: " + bucket.getRetentionPeriod());
    System.out.println("RetentionPolicyIsLocked: " + bucket.retentionPolicyIsLocked());
    System.out.println("RequesterPays: " + bucket.requesterPays());
    System.out.println("SelfLink: " + bucket.getSelfLink());
    System.out.println("StorageClass: " + bucket.getStorageClass().name());
    System.out.println("TimeCreated: " + bucket.getCreateTime());
    System.out.println("VersioningEnabled: " + bucket.versioningEnabled());
    if (bucket.getLabels() != null) {
      System.out.println("\n\n\nLabels:");
      for (Map.Entry<String, String> label : bucket.getLabels().entrySet()) {
        System.out.println(label.getKey() + "=" + label.getValue());
      }
    }
    if (bucket.getLifecycleRules() != null) {
      System.out.println("\n\n\nLifecycle Rules:");
      for (BucketInfo.LifecycleRule rule : bucket.getLifecycleRules()) {
        System.out.println(rule);
      }
    }
  }
}

Node.js

For more information, see the Cloud Storage Node.js API reference documentation.

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// Imports the Google Cloud client library
const {Storage} = require('@google-cloud/storage');

// Creates a client
const storage = new Storage();

async function getBucketMetadata() {
  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // The ID of your GCS bucket
  // const bucketName = 'your-unique-bucket-name';

  // Get Bucket Metadata
  const [metadata] = await storage.bucket(bucketName).getMetadata();

  console.log(JSON.stringify(metadata, null, 2));
}

PHP

For more information, see the Cloud Storage PHP API reference documentation.

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use Google\Cloud\Storage\StorageClient;

/**
 * Get bucket metadata.
 *
 * @param string $bucketName The name of your Cloud Storage bucket.
 *        (e.g. 'my-bucket')
 */
function get_bucket_metadata(string $bucketName): void
{
    $storage = new StorageClient();
    $bucket = $storage->bucket($bucketName);
    $info = $bucket->info();

    printf('Bucket Metadata: %s' . PHP_EOL, print_r($info));
}

Python

For more information, see the Cloud Storage Python API reference documentation.

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from google.cloud import storage


def bucket_metadata(bucket_name):
    """Prints out a bucket's metadata."""
    # bucket_name = 'your-bucket-name'

    storage_client = storage.Client()
    bucket = storage_client.get_bucket(bucket_name)

    print(f"ID: {bucket.id}")
    print(f"Name: {bucket.name}")
    print(f"Storage Class: {bucket.storage_class}")
    print(f"Location: {bucket.location}")
    print(f"Location Type: {bucket.location_type}")
    print(f"Cors: {bucket.cors}")
    print(f"Default Event Based Hold: {bucket.default_event_based_hold}")
    print(f"Default KMS Key Name: {bucket.default_kms_key_name}")
    print(f"Metageneration: {bucket.metageneration}")
    print(
        f"Public Access Prevention: {bucket.iam_configuration.public_access_prevention}"
    )
    print(f"Retention Effective Time: {bucket.retention_policy_effective_time}")
    print(f"Retention Period: {bucket.retention_period}")
    print(f"Retention Policy Locked: {bucket.retention_policy_locked}")
    print(f"Requester Pays: {bucket.requester_pays}")
    print(f"Self Link: {bucket.self_link}")
    print(f"Time Created: {bucket.time_created}")
    print(f"Versioning Enabled: {bucket.versioning_enabled}")
    print(f"Labels: {bucket.labels}")

Ruby

For more information, see the Cloud Storage Ruby API reference documentation.

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def get_bucket_metadata bucket_name:
  # The ID of your GCS bucket
  # bucket_name = "your-unique-bucket-name"

  require "google/cloud/storage"

  storage = Google::Cloud::Storage.new
  bucket  = storage.bucket bucket_name

  puts "ID:                       #{bucket.id}"
  puts "Name:                     #{bucket.name}"
  puts "Storage Class:            #{bucket.storage_class}"
  puts "Location:                 #{bucket.location}"
  puts "Location Type:            #{bucket.location_type}"
  puts "Cors:                     #{bucket.cors}"
  puts "Default Event Based Hold: #{bucket.default_event_based_hold?}"
  puts "Default KMS Key Name:     #{bucket.default_kms_key}"
  puts "Logging Bucket:           #{bucket.logging_bucket}"
  puts "Logging Prefix:           #{bucket.logging_prefix}"
  puts "Metageneration:           #{bucket.metageneration}"
  puts "Retention Effective Time: #{bucket.retention_effective_at}"
  puts "Retention Period:         #{bucket.retention_period}"
  puts "Retention Policy Locked:  #{bucket.retention_policy_locked?}"
  puts "Requester Pays:           #{bucket.requester_pays}"
  puts "Self Link:                #{bucket.api_url}"
  puts "Time Created:             #{bucket.created_at}"
  puts "Versioning Enabled:       #{bucket.versioning?}"
  puts "Index Page:               #{bucket.website_main}"
  puts "Not Found Page:           #{bucket.website_404}"
  puts "Labels:"
  bucket.labels.each do |key, value|
    puts " - #{key} = #{value}"
  end
  puts "Lifecycle Rules:"
  bucket.lifecycle.each do |rule|
    puts "#{rule.action} - #{rule.storage_class} - #{rule.age} - #{rule.matches_storage_class}"
  end
end

REST APIs

JSON API

1. Get an authorization access token from the OAuth 2.0 Playground. Configure the playground to use your own OAuth credentials. For instructions, see API authentication.

2. Use cURL to call the JSON API with a GET Bucket request:

   curl -X GET \
       -H "Authorization: Bearer OAUTH2_TOKEN" \
       "https://storage.googleapis.com/storage/v1/b/BUCKET_NAME?fields=cors"

   Where:

   • OAUTH2_TOKEN is the name of the access token you generated in Step 1.
   • BUCKET_NAME is the name of the relevant bucket. For example, my-bucket.

XML API

1. Get an authorization access token from the OAuth 2.0 Playground. Configure the playground to use your own OAuth credentials. For instructions, see API authentication.

2. Use cURL to call the XML API with a GET Bucket request:

   curl -X GET \
     -H "Authorization: Bearer OAUTH2_TOKEN" \
     "https://storage.googleapis.com/BUCKET_NAME?cors"

   Where:

   • OAUTH2_TOKEN is the name of the access token you generated in Step 1.
   • BUCKET_NAME is the name of the relevant bucket. For example, my-bucket.

Troubleshoot CORS requests

If you run into unexpected behavior when accessing Cloud Storage buckets from a different origin, try the following steps:

1. Review the CORS configuration on the target bucket. If you have multiple CORS configuration entries, make sure that the request values you use for troubleshooting map to values in a single CORS configuration entry.

2. Check that you are not making a request to the storage.cloud.google.com endpoint, which doesn't allow CORS requests. For more information about supported endpoints for CORS, see Cloud Storage CORS support.

3. Review a request and response using the tool of your choice. In a Chrome browser, you can use the standard developer tools to see this information:

   1. Click the Chrome menu on the browser toolbar.
   2. Select More Tools > Developer Tools.
   3. Click the Network tab.
   4. From your application or command line, send the request.
   5. In the pane displaying the network activity, locate the request.
   6. In the Name column, click the name corresponding to the request.
   7. Click the Headers tab to see the response headers, or the Response tab to see the content of the response.

   If you're not seeing a request and response, it is possible that your browser has cached an earlier failed preflight request attempt. Clearing your browser's cache should also clear the preflight cache. If it doesn't, set the MaxAgeSec value in your CORS configuration to a lower value (the default value is 1800 (30 minutes) if not specified), wait for however long the old MaxAgeSec was, then try the request again. This performs a new preflight request, which fetches the new CORS configuration and purges the cache entries. Once you have debugged your problem, raise MaxAgeSec back to a higher value, to reduce the preflight traffic to your bucket.

4. Ensure that the request has an Origin header and that the header value matches at least one of the Origins values in the bucket's CORS configuration. Note that the scheme, host, and port of the values must match exactly. Some examples of acceptable matches are as follows:

   • http://origin.example.com matches http://origin.example.com:80 (because 80 is the default HTTP port), but does not match https://origin.example.com, http://origin.example.com:8080, http://origin.example.com:5151, or http://sub.origin.example.com.

   • https://example.com:443 matches https://example.com but not http://example.com or http://example.com:443.

   • http://localhost:8080 only matches exactly http://localhost:8080, not http://localhost:5555 or http://localhost.example.com:8080.

5. Ensure that the HTTP method of the request (if this is a simple request), or the method specified in Access-Control-Request-Method (if this a preflight request), matches at least one of the Methods values in the bucket's CORS configuration.

6. If this is a preflight request, see if it includes one or more Access-Control-Request-Header headers. If so, then ensure that each Access-Control-Request-Header value matches a ResponseHeader value in the bucket's CORS configuration. All headers named in the Access-Control-Request-Header must be in the CORS configuration for the preflight request to succeed and include CORS headers in the response.

What's next

• Explore CORS configuration examples, including an example that removes the CORS configuration on a bucket.
• Learn more about CORS.