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Request Header

A request header is an HTTP header that can be used in an HTTP request to provide information about the request context, so that the server can tailor the response. For example, the Accept-* headers indicate the allowed and preferred formats of the response. Other headers can be used to supply authentication credentials (e.g. Authorization ), to control caching, or to get information about the user agent or referrer, etc.

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Request header

Not all headers that can appear in a request are referred to as request headers by the specification. For example, the Content-Type header is referred to as a representation header .

In addition, CORS defines a subset of request headers as simple headers , request headers that are always considered authorized and are not explicitly listed in responses to preflight requests.

The HTTP message below shows a few request headers after a GET request:

http 
                                    
                                        
                                            GET
                                            
                                                
                                                    /
                                                    home.html
                                                
                                            
                                            HTTP/1.1
                                        
                                        
                                            Host
                                            :
                                            developer.mozilla.org
                                        
                                        
                                            User-Agent
                                            :
                                            Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:50.0) Gecko/20100101 Firefox/50.0
                                        
                                        
                                            Accept
                                            :
                                            text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
                                        
                                        
                                            Accept-Language
                                            :
                                            en-US,en;q=0.5
                                        
                                        
                                            Accept-Encoding
                                            :
                                            gzip, deflate, br
                                        
                                        
                                            Referer
                                            :
                                            https://developer.mozilla.org/testpage.html
                                        
                                        
                                            Connection
                                            :
                                            keep-alive
                                        
                                        
                                            Upgrade-Insecure-Requests
                                            :
                                            1
                                        
                                        
                                            If-Modified-Since
                                            :
                                            Mon, 18 Jul 2016 02:36:04 GMT
                                        
                                        
                                            If-None-Match
                                            :
                                            "c561c68d0ba92bbeb8b0fff2a9199f722e3a621a"
                                        
                                        
                                            Cache-Control
                                            :
                                            max-age=0

See also

Updated on April 20, 2024 by Datarist.