HTTP: HTTP Request Headers

Every HTTP request has a set of mandatory and optional headers.

We have a lot of them, but here I’ll list you the most important / useful ones.

Host: flaviocopes.com

The domain name of the server, and the port number on which the server is listening. If the port is omitted, 80 is assumed.

This is the only mandatory HTTP request header

All the other headers are listed in alphabetical order.

Accept: application/json

The MIME type we’ll want the response to be

Accept-Charset: utf-8

Lists the charset we’ll want the response to be

Accept-Encoding: gzip, deflate

List of acceptable encodings we’ll want the response to be

Accept-Language: en-US

List of languages we’ll want the response to be

Authorization: Basic 34i3j4iom2323==

To pass authentication credentials, for example a token

We can set the caching rules using this header.

Cache-Control: no-cache tells the server to revalidate the data before sending the response to make sure it’s current
Cache-Control: max-age=30 tells the server we want data that’s not older than 30 seconds

Content-Length: 348

The length of the request body in bytes

Content-Type: application/x-www-form-urlencoded

The content type of the body of the request (used in POST and PUT requests).

Cookie: name=value

Sets a cookie

Referer: https://flaviocopes.com

The address of the previous web page from which a link to the currently requested page was followed.

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 (the browser)

0:	Introduction
1:	An HTTP request
2:	HTTP Methods
3:	HTTP Status Codes
4:	HTTP Client/Server communication
5:	▶︎ HTTP Request Headers
6:	HTTP Response Headers
7:	HTTPS
8:	HTTP/2
9:	HTTP/3