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Importance of Content Type in http

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Importance of Content-Type in HTTP

  • The content type status, part of an HTTP header, can tell a browser what type of content, e.g. a PNG image or an HTML page, is being transmitted.
    • This will affect the way a browser will process the file.
  • The content type, also called MIME (Multipurpose Internet Mail Extensions) or Media types, is a statement in the response header of the web server which gives the browser information regarding the format of a transmitted file.
    • This enables the browser to work faster, as the type of file does not have to be identified after the file has arrived.
    • attachments/Pasted image 20221107153020.jpg
Every non-empty response from a web server should contain a Content-Type
When should we use Content-Type
  • The client sets a content type for the body it is sending to the server (e.g. for Post or Put) to tell the server what type of data it is receiving.
  • The server sets a content type for the response.
What happens if I do not specify a content type?
  • If there is no indication as to the resource type of a file, the browser must find this out itself.
  • Most current browsers will read the first bytes of the file and try to compare them with the most common content types.
  • This can work well, but it does not always. Especially in the case of texts with unusual character encoding, it can lead to a browser recognising text but incorrectly reproducing the special characters that it contains.

  • There are sometimes instances in which the browser tries to recognise the content type even when that content has been defined.

    • This is called MIME sniffing, and it can be prevented with a special response header, the X-Content-Type-Options, through a nosniff directive.

  • The MIME type is always displayed as a combination of two pieces of information, one indicating what type of medium it is and the other the sub-type of the medium. It looks like this:

    • media type/sub-type
    • Example: text/css, text/javascript, text/xml, image/png, image/jpeg

  • application mime type:

    • The information communicated via application tells the browser that the files are to be opened with a certain programme.
    • The most interesting aspect is application/javascript, which indicates that a server-side javascript file is to be executed.
    • YouTube uses this MIME type for its video pages, as a JavaScript video player is integrated there which then takes care of loading and playing the actual video files.

  • Syntax: 

    Content-Type: text/html; charset=utf-8
Content-Type: multipart/form-data; boundary=something

References

Last updated: 2022-11-07