Description
The ServerSignature directive allows the configuration of a trailing footer line under server-generated documents (error messages, mod_proxy ftp directory listings, mod_info output, ...). The reason why you would want to enable such a footer line is that in a chain of proxies, the user often has no possibility to tell which of the chained servers actually produced a returned error message.
The Off setting, which is the default, suppresses the footer line (and is therefore compatible with the behavior of Apache-1.2 and below). The On setting simply adds a line with the server version number and ServerName of the serving virtual host, and the EMail setting additionally creates a "mailto:" reference to the ServerAdmin of the referenced document.
After version 2.0.44, the details of the server version number presented are controlled by the ServerTokens directive. This directive controls whether Server response header field which is sent back to clients includes a description of the generic OS-type of the server as well as information about compiled-in modules.
ServerTokens Full (or not specified)
Server sends (e.g.): Server: Apache/2.4.2 (Unix) PHP/4.2.2 MyMod/1.2
ServerTokens Prod[uctOnly]
Server sends (e.g.): Server: Apache
ServerTokens Major
Server sends (e.g.): Server: Apache/2
ServerTokens Minor
Server sends (e.g.): Server: Apache/2.4
ServerTokens Min[imal]
Server sends (e.g.): Server: Apache/2.4.2
ServerTokens OS
Server sends (e.g.): Server: Apache/2.4.2 (Unix)
This setting applies to the entire server, and cannot be enabled or disabled on a virtualhost-by-virtualhost basis.