List of Server Variables in asp.net

In the code behind use: Response.Output.WriteLine(Request.ServerVariables[variableName].ToString() to print the output of a particular server variables.

Variable Name	Description
ALL_HTTP	All HTTP headers sent by the client.
ALL_RAW	Retrieves all headers in raw form. The difference between ALL_RAW and ALL_HTTP is that ALL_HTTP places an HTTP_ prefix before the header name and the header name is always capitalized. In ALL_RAW the header name and values appear as they are sent by the client.
APPL_MD_PATH	Retrieves the metabase path for the Application for the ISAPI DLL.
APPL_PHYSICAL_PATH	Retrieves the physical path corresponding to the metabase path. IIS converts the APPL_MD_PATH to the physical (directory) path to return this value.
AUTH_PASSWORD	The value entered in the client's authentication dialog. This variable is available only if Basic authentication is used.
AUTH_TYPE	The authentication method that the server uses to validate users when they attempt to access a protected script.
AUTH_USER	The name of the user as it is derived from the authorization header sent by the client, before the user name is mapped to a Windows account. This variable is no different from REMOTE_USER. If you have an authentication filter installed on your Web server that maps incoming users to accounts, use LOGON_USER to view the mapped user name.
CERT_COOKIE	Unique ID for client certificate, returned as a string. Can be used as a signature for the whole client certificate.
CERT_FLAGS	bit0 is set to 1 if the client certificate is present.bit1 is set to 1 if the cCertification authority of the client certificate is invalid (it is not in the list of recognized CAs on the server).
CERT_ISSUER	Issuer field of the client certificate (O=MS, OU=IAS, CN=user name, C=USA).
CERT_KEYSIZE	Number of bits in Secure Sockets Layer connection key size. For example, 128.
CERT_SECRETKEYSIZE	Number of bits in server certificate private key. For example, 1024.
CERT_SERIALNUMBER	Serial number field of the client certificate.
CERT_SERVER_ISSUER	Issuer field of the server certificate.
CERT_SERVER_SUBJECT	Subject field of the server certificate.
CERT_SUBJECT	Subject field of the client certificate.
CONTENT_LENGTH	The length of the content as given by the client.
CONTENT_TYPE	The data type of the content. Used with queries that have attached information, such as the HTTP queries GET, POST, and PUT.
GATEWAY_INTERFACE	The revision of the CGI specification used by the server. The format is CGI/revision.
HTTP_<HeaderName>	The value stored in the header HeaderName. Any header other than those listed in this table must be prefixed by HTTP_ in order for the ServerVariables collection to retrieve its value.Note The server interprets any underscore (_) characters in HeaderName as dashes in the actual header. For example if you specify HTTP_MY_HEADER, the server searches for a header sent as MY-HEADER.
HTTP_ACCEPT	Returns the value of the Accept header.
HTTP_ACCEPT_LANGUAGE	Returns a string describing the language to use for displaying content.
HTTP_COOKIE	Returns the cookie string that was included with the request.
HTTP_HOST	Returns the name of the Web server. This may or may not be the same as SERVER_NAME depending on type of name resolution you are using on your Web server (IP address, host header).
HTTP_REFERER	Returns a string that contains the URL of the page that referred the request to the current page using an HTML <A> tag. Note that the URL is the one that the user typed into the browser address bar, which may not include the name of a default document.If the page is redirected, HTTP_REFERER is empty. HTTP_REFERER is not a mandatory member of the HTTP specification.
HTTP_USER_AGENT	Returns a string describing the browser that sent the request.
HTTPS	Returns ON if the request came in through secure channel (SSL) or it returns OFF if the request is for a non-secure channel.
HTTPS_KEYSIZE	Number of bits in Secure Sockets Layer connection key size. For example, 128.
HTTPS_SECRETKEYSIZE	Number of bits in server certificate private key. For example, 1024.
HTTPS_SERVER_ISSUER	Issuer field of the server certificate.
HTTPS_SERVER_SUBJECT	Subject field of the server certificate.
INSTANCE_ID	The ID for the IIS instance in textual format. If the instance ID is 1, it appears as a string. You can use this variable to retrieve the ID of the Web-server instance (in the metabase) to which the request belongs.
INSTANCE_META_PATH	The metabase path for the instance of IIS that responds to the request.
LOCAL_ADDR	Returns the Server Address on which the request came in. This is important on multi-homed computers where there can be multiple IP addresses bound to the computer and you want to find out which address the request used.
LOGON_USER	The Windows account that the user is impersonating while connected to your Web server. Use REMOTE_USER orAUTH_US<CODE>ER to view the raw user name that is contained in the request header. The only time LOGON_USER holds a different value than these other variables is if you have an authentication filter installed.
PATH_INFO	Extra path information as given by the client. You can access scripts by using their virtual path and the PATH_INFO server variable. If this information comes from a URL, it is decoded by the server before it is passed to the CGI script.
PATH_TRANSLATED	A translated version of PATH_INFO that takes the path and performs any necessary virtual-to-physical mapping.
QUERY_STRING	Query information stored in the string following the question mark (?) in the HTTP request.
REMOTE_ADDR	The IP address of the remote host making the request.
REMOTE_HOST	The name of the host making the request. If the server does not have this information, it will set REMOTE_ADDR and leave this empty.
REMOTE_USER	The name of the user as it is derived from the authorization header sent by the client, before the user name is mapped to a Windows account. If you have an authentication filter installed on your Web server that maps incoming users to accounts, useLOGON_USER to view the mapped user name.
REQUEST_METHOD	The method used to make the request. For HTTP, this is GET, HEAD, POST, and so on.
SCRIPT_NAME	A virtual path to the script being executed. This is used for self-referencing URLs.
SERVER_NAME	The server's host name, DNS alias, or IP address as it would appear in self-referencing URLs.
SERVER_PORT	The port number to which the request was sent.
SERVER_PORT_SECURE	A string that contains either 0 or 1. If the request is being handled on the secure port, then this will be 1. Otherwise, it will be 0.
SERVER_PROTOCOL	The name and revision of the request information protocol. The format is protocol/revision.
SERVER_SOFTWARE	The name and version of the server software that answers the request and runs the gateway. The format is name/version.
URL	Gives the base portion of the URL.

• Reference: Fernando Finelli