HTTP Headers Checker

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HTTP headers let the client and the server pass additional information with an HTTP request or response. An HTTP header consists of its case-insensitive name followed by a colon (:), then by its value. Whitespace before the value is ignored.

Custom proprietary headers have historically been used with an X- prefix, but this convention was deprecated in June 2012 because of the inconveniences it caused when nonstandard fields became standard in RFC 6648; others are listed in an IANA registry, whose original content was defined in RFC 4229. IANA also maintains a registry of proposed new HTTP headers.

Headers can be grouped according to their contexts:

  • General headers apply to both requests and responses, but with no relation to the data transmitted in the body.
  • Request headers contain more information about the resource to be fetched, or about the client requesting the resource.
  • Response headers hold additional information about the response, like its location or about the server providing it.
  • Entity headers contain information about the body of the resource, like its content length or MIME type.

Headers can also be grouped according to how proxies handle them:

  • Connection
  • Keep-Alive
  • Proxy-Authenticate
  • Proxy-Authorization
  • TE
  • Trailer
  • Transfer-Encoding
  • Upgrade.

End-to-end headersThese headers must be transmitted to the final recipient of the message: the server for a request, or the client for a response. Intermediate proxies must retransmit these headers unmodified and caches must store them.Hop-by-hop headersThese headers are meaningful only for a single transport-level connection, and must not be retransmitted by proxies or cached. Note that only hop-by-hop headers may be set using the Connection general header.