The HTTP Request Headers List
Every HTTP request has a set of mandatory and optional headers. This post aims to list all those headers, and describe them.
- Standard headers
- A-IM
- Accept
- Accept-Charset
- Accept-Encoding
- Accept-Language
- Accept-Datetime
- Access-Control-Request-Method
- Access-Control-Request-Headers
- Authorization
- Cache-Control
- Connection
- Content-Length
- Content-Type
- Cookie
- Date
- Expect
- Forwarded
- From
- Host
- If-Match
- If-Modified-Since
- If-None-Match
- If-Range
- If-Unmodified-Since
- Max-Forwards
- Origin
- Pragma
- Proxy-Authorization
- Range
- Referer
- TE
- User-Agent
- Upgrade
- Via
- Warning
- Non-standard headers
Standard headers
A-IM
A-IM: feed
Instance manipulations that are acceptable in the response. Defined in RFC 3229
Accept
Accept: application/json
The media type/types acceptable
Accept-Charset
Accept-Charset: utf-8
The charset acceptable
Accept-Encoding
Accept-Encoding: gzip, deflate
List of acceptable encodings
Accept-Language
Accept-Language: en-US
List of acceptable languages
Accept-Datetime
Accept-Datetime: Thu, 31 May 2007 20:35:00 GMT
Request a past version of the resource prior to the datetime passed
Access-Control-Request-Method
Access-Control-Request-Method: GET
Used in a CORS request
Access-Control-Request-Headers
Access-Control-Request-Headers: origin, x-requested-with, accept
Used in a CORS request
Authorization
Authorization: Basic 34i3j4iom2323==
HTTP basic authentication credentials
Cache-Control
Cache-Control: no-cache
Set the caching rules
Connection
Connection: keep-alive
Control options for the current connection. Accepts keep-alive
and close
. Deprecated in HTTP/2
Content-Length
Content-Length: 348
The length of the request body in bytes
Content-Type
Content-Type: application/x-www-form-urlencoded
The content type of the body of the request (used in POST and PUT requests).
Cookie
Cookie: name=value
Date
Date: Tue, 15 Nov 1994 08:12:31 GMT
The date and time that the request was sent
Expect
Expect: 100-continue
It’s typically used when sending a large request body. We expect the server to return back a 100 Continue
HTTP status if it can handle the request, or 417 Expectation Failed
if not
Forwarded
Forwarded: for=192.0.2.60; proto=http; by=203.0.113.43
Disclose original information of a client connecting to a web server through an HTTP proxy. Used for testing purposes only, as it discloses privacy sensitive information
From
From: user@example.com
The email address of the user making the request. Meant to be used, for example, to indicate a contact email for bots.
Host
Host: flaviocopes.com
The domain name of the server (used to determined the server with virtual hosting), and the TCP port number on which the server is listening. If the port is omitted, 80 is assumed. This is a mandatory HTTP request header
If-Match
If-Match: "737060cd8c284d8582d"
Given one (or more) ETags
, the server should only send back the response if the current resource matches one of those ETags. Mainly used in PUT methods to update a resource only if it has not been modified since the user last updated it
If-Modified-Since
If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT
Allows to return a 304 Not Modified
response header if the content is unchanged since that date
If-None-Match
If-None-Match: "737060cd882f209582d"
Allows a 304 Not Modified
response header to be returned if content is unchanged. Opposite of If-Match
.
If-Range
If-Range: "737060cd8c9582d"
Used to resume downloads, returns a partial if the condition is matched (ETag or date) or the full resource if not. See more
If-Unmodified-Since
If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT
Only send the response if the entity has not been modified since the specified time
Max-Forwards
Max-Forwards: 10
Limit the number of times the message can be forwarded through proxies or gateways
Origin
Origin: http://mydomain.com
Send the current domain to perform a CORS request, used in an OPTIONS HTTP request (to ask the server for Access-Control- response headers)
Pragma
Pragma: no-cache
Used for backwards compatibility with HTTP/1.0 caches
Proxy-Authorization
Proxy-Authorization: Basic 2323jiojioIJOIOJIJ==
Authorization credentials for connecting to a proxy
Range
Range: bytes=500-999
Request only a specific part of a resource
Referer
Referer: https://flaviocopes.com
The address of the previous web page from which a link to the currently requested page was followed.
TE
TE: trailers, deflate
Specify the encodings the client can accept. Accepted values: compress
, deflate
, gzip
, trailers
. Only trailers
is supported in HTTP/2
User-Agent
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36
The string that identifies the user agent
Upgrade
Upgrade: h2c, HTTPS/1.3, IRC/6.9, RTA/x11, websocket
Ask the server to upgrade to another protocol. Deprecated in HTTP/2
Via
Via: 1.0 fred, 1.1 example.com (Apache/1.1)
Informs the server of proxies through which the request was sent
Warning
Warning: 199 Miscellaneous warning
A general warning about possible problems with the status of the message. Accepts a special range of values.
Non-standard headers
There are some widely used non-standard headers as well, including:
Dnt
DNT: 1
If enabled, asks servers to not track the user
X-Requested-With
X-Requested-With: XMLHttpRequest
Identifies XHR requests
X-CSRF-Token
X-CSRF-Token: <TOKEN>
Used to prevent CSRF
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