If you enable versioning for a bucket, Amazon S3 automatically generates a unique version ID for the object being stored. Amazon S3 returns this ID in the response using the x-amz-version-id response header. If versioning is suspended, Amazon S3 always uses null as the version ID for the object stored. For more information about returning the versioning state of a bucket, see GET Bucket (Versioning Status).

If you enable versioning on a bucket, when Amazon S3 receives multiple write requests for the same object simultaneously, all of the objects will be stored.

To see sample requests that use versioning, see Sample Request.