Common Response Headers - Amazon Simple Storage Service

Common Response Headers

The following table describes response headers that are common to most Amazon S3 responses.

Name Description
Access-Control-Allow-Credentials

A Boolean that determines if the server allows CORS requests to contain credentials. If the Access-Control-Allow-Origin request header is set to '*' then the Access-Control-Allow-Credentials response header will be omitted, else it is set to true when CORS evaluation is successful.

Type: Boolean

Default: None
Access-Control-Allow-Headers

A list of HTTP headers allowed for your CORS requests. The Access-Control-Allow-Headers response header is returned for successful CORS evaluations and explicitly specifies all allowed Access-Control-Request-Headers.

Type: String

Default: None
Access-Control-Allow-Methods

A list that specifies which HTTP methods are allowed. Amazon S3 will only allow CORS requests from allowed CORS methods when the CORS evaluation is successful.

Type: String

Default: None
Access-Control-Allow-Origin

The location of the allowed origin. Amazon S3 will only send the Access-Control-Allow-Origin response header when the CORS evaluation is successful. If the request origin matches '*' in the CORS configuration's allowed origins then the '*' is returned in this response header instead of the original origin.

Type: String

Default: None
Access-Control-Expose-Headers

A list that allows a server to identify a response header that exposes access for applications when the CORS evaluation is successful.

Type: String

Default: None
Access-Control-Max-Age

The time in seconds that your browser can cache the response for a CORS pre-flight request as identified by the resource, the HTTP method, and the origin. The Access-Control-Max-Age response header is only returned when the CORS evaluation is successful.

Type: Integer

Default: None
Vary

A list that indicates which request headers the CORS evaluation result varies on. The Vary response header is only returned when the CORS evaluation is successful.

Type: String

Default: None
Content-Length

The length in bytes of the body in the response.

Type: String

Default: None
Content-Type

The MIME type of the content. For example, Content-Type: text/html; charset=utf-8.

Type: String

Default: None
Connection

A value that specifies whether the connection to the server is open or closed.

Type: Enum

Valid Values: open | close

Default: None
Date

The date and time that Amazon S3 responded; for example, Wed, 01 Mar 2006 12:00:00 GMT.

Type: String

Default: None
ETag

The entity tag (ETag) represents a specific version of the object. The ETag reflects changes only to the contents of an object, not its metadata. The ETag might or might not be an MD5 digest of the object data. Whether or not it is depends on how the object was created and how it is encrypted, as follows:

  • Objects created through the AWS Management Console or by the PUT Object, POST Object, or Copy operation:

    • Objects that are plaintext or encrypted by server-side encryption with Amazon S3 managed keys (SSE-S3) have ETags that are an MD5 digest of their data.

    • Objects encrypted by server-side encryption with customer-provided keys (SSE-C) or AWS Key Management Service (AWS KMS) keys (SSE-KMS) have ETags that are not an MD5 digest of their object data.

  • Objects created by either the Multipart Upload or Upload Part Copy operation have ETags that are not MD5 digests, regardless of the method of encryption.

Type: String
Server

The name of the server that created the response.

Type: String

Default: AmazonS3

x-amz-delete-marker

A value that specifies whether the object returned was (true) or was not (false) a delete marker.

Type: Boolean

Valid Values: true | false

Default: false
x-amz-id-2

A special token that is used together with the x-amz-request-id header to help AWS troubleshoot problems. For information about AWS Support using these request IDs, see Troubleshooting Amazon S3.

Type: String

Default: None
x-amz-request-id

A value created by Amazon S3 that uniquely identifies the request. This value is used together with the x-amz-id-2 header to help AWS troubleshoot problems. For information about AWS Support using these request IDs, see Troubleshooting Amazon S3.

Type: String

Default: None
x-amz-server-side-encryption

The server-side encryption algorithm used when storing this object in Amazon S3 (for example, AES256, aws:kms).

Valid Values: AES256 | aws:kms
x-amz-version-id

The version of the object. When you enable versioning, Amazon S3 generates a random number for objects added to a bucket. The value is UTF-8 encoded and URL ready. When you PUT an object in a bucket where versioning has been suspended, the version ID is always null.

Type: String

Valid Values: null | any URL-ready, UTF-8 encoded string

Default: null