An entity tag (ETag) is an identifier assigned by a web server to a specific version of a resource found at a URL. This header field makes the request method conditional on ETags.
ETags
Key name of the object.
If present, the objects are deleted only if its modification times matches the provided Timestamp.
Timestamp
If present, the objects are deleted only if its size matches the provided size in bytes.
Version ID for the specific version of the object to delete.