HTTP/1.1 Request Headers

HTTP headerQuick definitionAgent
Acceptmedia types handled by clientClient
Accept-Charsetcharsets understood by clientClient
Accept-Encodingencodings understood by clientClient
Accept-Languagelanguages understood by client (or ideally by user)Client
Accept-Rangeswhether server understands range requests (and what type)Server
Agehow long the content has been cachedCache
Allowmethods supported for that URLServer
Authori­zationHTTP authen­tication user name and passwordClient
Cache-Controlvarious sub-fields indicating if the file can be cachedServer
ConnectionTo distinguish persistent and close-able connectionsClient, Server
Content-EncodingEncodings used - for example gzip compressionServer
Content-LanguageLanguage of pageServer
Content-LengthSize of what is being sent from server or POSTed by UAClient, Server
Content-LocationThe "real" URL of a pageServer
Content-MD5MD5 hash for integrity check of the entity-bodyClient, Server
Content-RangeWhat part of the document is being sentServer
Content-TypeWhat type of file is sentServer
DateCurrent dateServer
ETagShort "signature" of that version of a file, can be used to check if it is updatedServer
ExpectClient asks for specific server behaviourClient
Expireshow long the content may be cachedServer
FromE-mail of user visiting site (anyone actually using this??)Client
HostDomain name of server one is requesting page fromClient
If-MatchIf page still matches previously received ETag "signature"Client
If-Modified-SinceIf page has been changed since a certain dateClient
If-None-MatchIf page does not match previously received ETag "signature"Client
If-RangeRequest only part of a file if it isn't updatedClient
If-Unmod­ified-SinceIf page hasn't been changed since a certain dateClient
Last-ModifiedDate of last time the file was changedServer
LocationSend the request to another placeServer
Max-ForwardsLimit the number of proxy servers that may process the requestClient
PragmaGeneral "whatever" tag, like HTML's METAClient, Server, Cache
Proxy-Authen­ticateRequest proxy user name and passwordProxy
Proxy-Authori­zationSend proxy user name and passwordClient
RangeRequest only part of a fileClient
RefererURL of page with a link that took you to the currentClient
Retry-AfterUsed with error messages to indicate when service may be available againServer
ServerName of server softwareServer
TEAcceptable transfer-codingsClient
TrailerUsed with transfer-coding to show what HTTP headers are available in "trailer" of messageServer
Transfer-EncodingType of transformation used between sender and recipientServer
UpgradeClient indicates that it supports other protocols/versions than HTTP/1.1Client
User-AgentName of UA softwareClient
VaryFor content-negotiation, shows criteria used for selecting that contentServer
ViaProxy servers note that they've been involved in transferring this contentProxy
WarningHuman- or proxy-readable message about the state of the contentsServer
WWW-Authen­ticateRequest user name and passwordServer
Modified from Hallvord's original cheatsheet for the HTTP 1.1 specification