# Common response headers
<a name="RESTCommonResponseHeaders"></a>

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` \$1 `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: [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/AmazonS3/latest/API/RESTCommonResponseHeaders.html) 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` \$1 `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 Support using these request IDs, see [ Troubleshooting Amazon S3](https://docs.aws.amazon.com/AmazonS3/latest/userguide/troubleshooting.html#get-request-ids). 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 Support using these request IDs, see [ Troubleshooting Amazon S3](https://docs.aws.amazon.com/AmazonS3/latest/userguide/troubleshooting.html#get-request-ids). 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` \$1 `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` \$1 any URL-ready, UTF-8 encoded string Default: null  |