Class HeadObjectCommandProtected

The HEAD action retrieves metadata from an object without returning the object itself. This action is useful if you're only interested in an object's metadata. To use HEAD, you must have READ access to the object.

A HEAD request has the same options as a GET action 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 404 Not Found or 403 Forbidden code. It is not possible to retrieve the exact exception beyond these error codes.

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:

• 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).

• Encryption request headers, like x-amz-server-side-encryption, should not be sent for GET requests if your object uses server-side encryption with KMS keys (SSE-KMS) or server-side encryption with Amazon S3–managed encryption keys (SSE-S3). If your object does use these types of keys, you’ll get an HTTP 400 BadRequest error.

• The last modified property in this case is the creation date of the object.

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

Consider the following when using request headers:

• Consideration 1 – If both of the If-Match and If-Unmodified-Since headers are present in the request as follows:

  • If-Match condition evaluates to true, and;

  • If-Unmodified-Since condition evaluates to false;

  Then Amazon S3 returns 200 OK and the data requested.

• Consideration 2 – If both of the If-None-Match and If-Modified-Since headers are present in the request as follows:

  • If-None-Match condition evaluates to false, and;

  • If-Modified-Since condition evaluates to true;

  Then Amazon S3 returns the 304 Not Modified response code.

For more information about conditional requests, see RFC 7232.

Permissions

You need the relevant read object (or version) permission for this operation. For more information, see Specifying Permissions in a Policy. If the object you request does not exist, the error 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 ("no such key") error.

• If you don’t have the s3:ListBucket permission, Amazon S3 returns an HTTP status code 403 ("access denied") error.

The following actions are related to HeadObject:

• GetObject

• GetObjectAttributes

Example

Use a bare-bones client and the command you need to make an API call.

import { S3Client, HeadObjectCommand } from "@aws-sdk/client-s3"; // ES Modules import
// const { S3Client, HeadObjectCommand } = require("@aws-sdk/client-s3"); // CommonJS import
const client = new S3Client(config);
const command = new HeadObjectCommand(input);
const response = await client.send(command);

Param

HeadObjectCommandInput

Returns

HeadObjectCommandOutput

See

• HeadObjectCommandInput for command's input shape.
• HeadObjectCommandOutput for command's response shape.
• config for S3Client's config shape.

Throws

NotFound (client fault)

The specified content does not exist.

Example

To retrieve metadata of an object without returning the object itself

// The following example retrieves an object metadata.
const input = {
  "Bucket": "examplebucket",
  "Key": "HappyFace.jpg"
};
const command = new HeadObjectCommand(input);
const response = await client.send(command);
/* response ==
{
  "AcceptRanges": "bytes",
  "ContentLength": "3191",
  "ContentType": "image/jpeg",
  "ETag": "\"6805f2cfc46c0f04559748bb039d69ae\"",
  "LastModified": "Thu, 15 Dec 2016 01:19:41 GMT",
  "Metadata": {},
  "VersionId": "null"
}
*/
// example id: to-retrieve-metadata-of-an-object-without-returning-the-object-itself-1481834820480