Hypertext Transfer Protocol Headers  
Request Headers Description
Accept The content types that are acceptable
Accept-Charset The character sets that are acceptable
Accept-Encoding The encoding types that are acceptable, used for data compression
Accept-Language The languages that are acceptable
Authorization Authentication credentials for the client session
Connection Determines if the connection to the server should be persistent
Cookie A cookie that was previously sent by the server
Content-Length The length of the request data in bytes
Content-MD5 A base64 encoded MD5 message digest of the request data
Date The date and time that the request was made
Host The host name and optional port number used to connect to the server
If-Modified-Since Return a resource only if it has been modified since the requested date and time
If-Unmodified-Since Return a resource only if it has not been modified since the requested date and time
Pragma Implementation specific header, typically used to control caching
Proxy-Authorization Authentication credentials used when connecting through a proxy server
Range Request a specific range of bytes from the resource
Referer The address of the previous document or other resource that linked to the current document
User-Agent Identifies the client application that has issued the request
Via Identifies the proxy server that forwarded the request
Response Headers Description
Accept-Ranges Used to indicate if the server accepts returning partial content
Age The age that a document has been in a proxy cache, in seconds
Allow A list of methods that are allowed for the specified resource
Cache-Control How the resource should be cached by the client
Connection How the connection should be managed
Content-Encoding The type of encoding used for the data return to the client, used with compression
Content-Language The language used in the response to the client
Content-Location An alternate location for the specified resource
Content-MD5 A base64 encoded MD5 message digest of the response data
Content-Disposition Used to indicate that the content being returned is a downloaded file
Content-Range The range of bytes returned by the server for partially downloaded data
Content-Type The MIME type that identifies the data being returned by the server
Date The date and time the response was sent by the server
ETag A unique identifier for a specific version of a resource, typically a message digest
Expires The date and time which the response is considered stale
Last-Modified The date and time the resource was last modified on the server
Location The new location of the requested resource, used with redirection
Pragma Implementation specific header, typically used to control caching
Retry-After The number of seconds the client should wait before trying again if a resource is unavailable
Server Identifies the server, typically including the server name, version and operating system
Set-Cookie A cookie that should be returned by the client on subsequent requests to the server
Transfer-Encoding Encoding method used to transfer the data to the client
Via Informs the client of the proxy server that the request was sent through
WWW-Authenticate The authentication scheme the client should use to access the resource