[转]difference between accept and content-type http headers

Q:
So the accept header tells the server the mime-type of the resource the browser is looking for. For example, the server can send plain text, html, json, etc. Ok that makes sense. But then I look at the content-type header and it looks to be doing the same thing. For example, it tells the server that it wants text or json. So then what's the difference?

A:
As you correctly note, the Accept header is used by HTTP clients to tell the server what content types they'll accept. The server will then send back a response, which will include a Content-Type header telling the client what the content type of the returned content actually is.

However, as you may have noticed, HTTP requests can also contain Content-Type headers. Why? Well, think about POST or PUT requests. With those request types, the client is actually sending a bunch of data to the server as part of the request, and the Content-Type header tells the server what the data actually is (and thus determines how the server will parse it).

In particular, for a typical POST request resulting from an HTML form submission, the Content-Type of the request will normally be either application/x-www-form-urlencoded or multipart/form-data.

参考:
http://webmasters.stackexchange.com/questions/31212/difference-between-accept-and-content-type-http-headers