AWS SDK Version 3 for .NET
API Reference

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The HEAD operation retrieves metadata from an object without returning the object itself. This operation is useful if you're interested only in an object's metadata.

A HEAD request has the same options as a GET operation on an object. The response is identical to the GET response except that there is no response body. Because of this, if the HEAD request generates an error, it returns a generic code, such as 400 Bad Request, 403 Forbidden, 404 Not Found, 405 Method Not Allowed, 412 Precondition Failed, or 304 Not Modified. It's not possible to retrieve the exact exception of these error codes.

Request headers are limited to 8 KB in size. For more information, see Common Request Headers.

Permissions
  • General purpose bucket permissions - To use HEAD, you must have the s3:GetObject permission. You need the relevant read object (or version) permission for this operation. For more information, see Actions, resources, and condition keys for Amazon S3 in the Amazon S3 User Guide. For more information about the permissions to S3 API operations by S3 resource types, see Required permissions for Amazon S3 API operations in the Amazon S3 User Guide.

    If the object you request doesn't exist, the error that Amazon S3 returns depends on whether you also have the s3:ListBucket permission.

    • If you have the s3:ListBucket permission on the bucket, Amazon S3 returns an HTTP status code 404 Not Found error.

    • If you don’t have the s3:ListBucket permission, Amazon S3 returns an HTTP status code 403 Forbidden error.

  • Directory bucket permissions - To grant access to this API operation on a directory bucket, we recommend that you use the CreateSession API operation for session-based authorization. Specifically, you grant the s3express:CreateSession permission to the directory bucket in a bucket policy or an IAM identity-based policy. Then, you make the CreateSession API call on the bucket to obtain a session token. With the session token in your request header, you can make API requests to this operation. After the session token expires, you make another CreateSession API call to generate a new session token for use. Amazon Web Services CLI or SDKs create session and refresh the session token automatically to avoid service interruptions when a session expires. For more information about authorization, see CreateSession.

    If you enable x-amz-checksum-mode in the request and the object is encrypted with Amazon Web Services Key Management Service (Amazon Web Services KMS), you must also have the kms:GenerateDataKey and kms:Decrypt permissions in IAM identity-based policies and KMS key policies for the KMS key to retrieve the checksum of the object.

Encryption

Encryption request headers, like x-amz-server-side-encryption, should not be sent for HEAD requests if your object uses server-side encryption with Key Management Service (KMS) keys (SSE-KMS), dual-layer server-side encryption with Amazon Web Services KMS keys (DSSE-KMS), or server-side encryption with Amazon S3 managed encryption keys (SSE-S3). The x-amz-server-side-encryption header is used when you PUT an object to S3 and want to specify the encryption method. If you include this header in a HEAD request for an object that uses these types of keys, you’ll get an HTTP 400 Bad Request error. It's because the encryption method can't be changed when you retrieve the object.

If you encrypt an object by using server-side encryption with customer-provided encryption keys (SSE-C) when you store the object in Amazon S3, then when you retrieve the metadata from the object, you must use the following headers to provide the encryption key for the server to be able to retrieve the object's metadata. The headers are:

  • x-amz-server-side-encryption-customer-algorithm

  • x-amz-server-side-encryption-customer-key

  • x-amz-server-side-encryption-customer-key-MD5

For more information about SSE-C, see Server-Side Encryption (Using Customer-Provided Encryption Keys) in the Amazon S3 User Guide.

Directory bucket - For directory buckets, there are only two supported options for server-side encryption: SSE-S3 and SSE-KMS. SSE-C isn't supported. For more information, see Protecting data with server-side encryption in the Amazon S3 User Guide.

Versioning
  • If the current version of the object is a delete marker, Amazon S3 behaves as if the object was deleted and includes x-amz-delete-marker: true in the response.

  • If the specified version is a delete marker, the response returns a 405 Method Not Allowed error and the Last-Modified: timestamp response header.

  • Directory buckets - Delete marker is not supported for directory buckets.

  • Directory buckets - S3 Versioning isn't enabled and supported for directory buckets. For this API operation, only the null value of the version ID is supported by directory buckets. You can only specify null to the versionId query parameter in the request.

HTTP Host header syntax

Directory buckets - The HTTP Host header syntax is Bucket_name.s3express-az_id.region.amazonaws.com.

For directory buckets, you must make requests for this API operation to the Zonal endpoint. These endpoints support virtual-hosted-style requests in the format https://bucket_name.s3express-az_id.region.amazonaws.com/key-name. Path-style requests are not supported. For more information, see Regional and Zonal endpoints in the Amazon S3 User Guide.

The following actions are related to HeadObject:

Note:

For .NET Core this operation is only available in asynchronous form. Please refer to GetObjectMetadataAsync.

Namespace: Amazon.S3
Assembly: AWSSDK.S3.dll
Version: 3.x.y.z

Syntax

C#
public virtual GetObjectMetadataResponse GetObjectMetadata(
         String bucketName,
         String key,
         String versionId
)

Parameters

bucketName
Type: System.String

The name of the bucket that contains the object. Directory buckets - When you use this operation with a directory bucket, you must use virtual-hosted-style requests in the format Bucket_name.s3express-az_id.region.amazonaws.com. Path-style requests are not supported. Directory bucket names must be unique in the chosen Availability Zone. Bucket names must follow the format bucket_base_name--az-id--x-s3 (for example, DOC-EXAMPLE-BUCKET--usw2-az1--x-s3). For information about bucket naming restrictions, see Directory bucket naming rules in the Amazon S3 User Guide. Access points - When you use this action with an access point, you must provide the alias of the access point in place of the bucket name or specify the access point ARN. When using the access point ARN, you must direct requests to the access point hostname. The access point hostname takes the form AccessPointName-AccountId.s3-accesspoint.Region.amazonaws.com. When using this action with an access point through the Amazon Web Services SDKs, you provide the access point ARN in place of the bucket name. For more information about access point ARNs, see Using access points in the Amazon S3 User Guide. Access points and Object Lambda access points are not supported by directory buckets. S3 on Outposts - When you use this action with Amazon S3 on Outposts, you must direct requests to the S3 on Outposts hostname. The S3 on Outposts hostname takes the form AccessPointName-AccountId.outpostID.s3-outposts.Region.amazonaws.com. When you use this action with S3 on Outposts through the Amazon Web Services SDKs, you provide the Outposts access point ARN in place of the bucket name. For more information about S3 on Outposts ARNs, see What is S3 on Outposts? in the Amazon S3 User Guide.

key
Type: System.String

The object key.

versionId
Type: System.String

Version ID used to reference a specific version of the object. For directory buckets in this API operation, only the null value of the version ID is supported.

Return Value


The response from the GetObjectMetadata service method, as returned by S3.

Version Information

.NET Framework:
Supported in: 4.5 and newer, 3.5

See Also