HTTP Headers - Report By Lakshitha Geethmal

  

HTTP Headers 

Report of HTTP Headers & Uses

Meaning of HTTP Headers

HTTP headers are name or value pairs presented in the request and response messages of Hypertext Transfer Protocol message headers (HTTP). In most cases, a single colon separates the header name from the value. HTTP headers are used in both requests and replies.

HTTP headers are the code that allows data to be sent from a Web server to a client. HTTP headers are mostly used for communication in both directions between the server and the client.

HTTP Headers uses

Through the request and response headers, HTTP headers are used to communicate extra information between clients and servers. All header fields are separated by a colon, and key-value pairs are stored in clear-text string format.

In terms of context, there are four different types of headers:

1.      General Header: This type of header is applied on Request and Response headers both but without affecting the database body.

These headers contain directives that need to be followed, for both the requester and receiver. This can include information regarding:

·        Caching directives.

·        Specified connection options.

·        The date (always listed in Greenwich Mean Time)

·        Pragma

·        Upgrade (for if the protocols need to be switched)

·        Via (to indicate intermediate protocols)

·        Warning (for additional information not found elsewhere in the header. There may be more than one warning listed.)

 

2.      Request Header: This type of header contains information about the fetched request by the client.

Whenever you type a URL into the address bar and try to access it, your browser sends an HTTP request to the server. The HTTP request header contains information in a text-record form, which includes particulars such as the:

·        Type, capabilities, and version of the browser that generates the request.

·        Operating system used by the client.

·        Page that was requested.

·        Various types of outputs accepted by the browser.

 

The HTTP Request Headers with Example

·        Accept

-        Ex. Accept: application/json (The media type/types acceptable)

·        Accept-Encoding

-        Ex. Accept-Encoding: gzip, deflate (List of acceptable encodings)

·        Accept-Language

-        Ex. Accept-Language: en-US (List of acceptable languages)

·        Accept-Datetime

-        Ex. Accept-Datetime: Thu, 31 May 2007 20:35:00 GMT (Request a past version of the resource prior to the DateTime passed)

·        Connection

-        Ex. Connection: keep-alive (Control options for the current connection. Accepts keep-alive and close. Deprecated in HTTP/2)

·        Date

-        Ex. Date: Tue, 15 Nov 1994 08:12:31 GMT (The date and time that the request was sent)

 

 

3.      Response Header: This type of headers contains the location of the source that has been requested by the client.

Upon receiving the request header, the Web server will send an HTTP response header back to the client. An HTTP response header includes information in a text-record form that a Web server transmits back to the client's browser. The response header contains particulars such as the type, date and size of the file sent back by the server, as well as information regarding the server.

The HTTP Response Headers with example

·        Accept-Patch

-        Ex. Accept-Patch: text/example;charset=utf-8 (Specifies which patch document formats this server supports)

·        Accept-Ranges

-        Ex. Accept-Ranges: bytes (What partial content range types of this server supports via byte serving)

·        Age

-        Ex. Age: 22 (The age the object has been in a proxy cache in seconds)

·        Allow

-        Ex. Allow: GET, POST, HEAD (Valid methods for a specified resource. To be used for a 405 Method not allowed)

·        Connection

-        Ex. Connection: close (Control options for the current connection and list of hop-by-hop response fields. Deprecated in HTTP/2)

·        Content-Encoding

-        Ex. Content-Encoding: gzip (The type of encoding used on the data. See HTTP compression)

 

4.      Entity Header: This type of headers contains the information about the body of the resources like MIME type, Content-length.

These headers include information regarding:

·        Allow (methods supported by the identified resource)

·        Content Encoding.

·        Content Language.

·        Content Location.

·        Content Length.

·        MD-5 (for checking the integrity of the message upon receipt).

·        Content-Range.

·        Content Type.

·        When it Expires.

·        When it was last modified.

 

Ref: ( https://www.cleantutorials.com/wp-content/uploads/2015/11/http-header-and-body.png)

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

·        Connection

·        Keep-Alive

·        Proxy-Authenticate

·        Proxy-Authorization

·        TE

·        Trailer

·        Transfer-Encoding

 

End-to-end headers

These 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 headers

These 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 header.