HTTP Headers

About

HTTP headers let the client and the server pass additional information with a message in a request or response¹. The HTTP headers for a server’s response, and about the server that sent it². This information can assist the client with displaying the response to a user, with storing (or caching) the response for future use, and with making further requests to the server now in the future. They communicate core information, such as what browser the client is using and what data is being requested. They contain text information stored in key-value pairs, and are included in every HTTP request and response.

Headers differences between HTTP/1.X and HTTP/2 and above

In HTTP/1.X, a headers is a case-insensitive name followed by a colon, then optional whitespace which will be ignored, and finally by its value (for example: Allow: POST). In HTTP/2 and above, headers are displayed in lowercase when viewed in developer tools (:accept: */*), and prefixed with a colon for a special group of pseudo-headers (status: 200). For more information, see HTTP messages.

Headers groupings

Headers are grouped according to their contexts:

• HTTP request headers
• HTTP response headers
• Representation headers
• Payload headers
• End-to-end headers
• Hop-by-hop headers

Headers types

• Authentication headers
• Caching headers
• Conditionals headers
• Connection management headers
• Content negotiation headers
• Controls headers
• Cookies headers
• CORS headers
• Downloads headers
• Integrity digests headers
• Message body information headers
• Preferences headers
• Proxies headers
• Range requests headers
• Redirects headers
• Request context headers
• Response context headers
• Security headers
• Fetch metadata request headers
• Server-sent events headers
• Transfer coding headers
• Web Sockets headers
• Other headers
  • Alt-Svc header
  • Alt-Used header
  • Date header
  • Link header
  • Retry-After header
  • Server-Timing header
  • Service-Work header
  • Service-Worker-Allowed header
  • SourceMap header
  • Upgrade header
  • Priority header

Anki

Links

• Hypertext Transfer Protocol (HTTP)

References