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Content-Type

Content-Type

The Content-Type representation header is used to indicate the original media type of the resource (prior to any content encoding applied for sending).

In responses, a Content-Type header provides the client with the actual content type of the returned content. This header's value may be ignored, for example when browsers perform MIME sniffing; set the X-Content-Type-Options header value to nosniff to prevent this behavior.

In requests, (such as POST or PUT), the client tells the server what type of data is actually sent.

Header type Representation header
Forbidden header name no
CORS-safelisted response header yes
CORS-safelisted request header yes, with the additional restriction that values can't contain a CORS-unsafe request header byte: 0x00-0x1F (except 0x09 (HT)), "():<>?@[\]{}, and 0x7F (DEL).
It also needs to have a MIME type of its parsed value (ignoring parameters) of either application/x-www-form-urlencoded, multipart/form-data, or text/plain.

Syntax

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

Directives

media-type

The MIME type of the resource or the data.

charset

The character encoding standard.

boundary

For multipart entities the boundary directive is required. The directive consists of 1 to 70 characters from a set of characters (and not ending with white space) known to be very robust through email gateways. It is used to encapsulate the boundaries of the multiple parts of the message. Often, the header boundary is prepended with two dashes and the final boundary has two dashes appended at the end.

Examples

Content-Type in HTML forms

In a POST request, resulting from an HTML form submission, the Content-Type of the request is specified by the enctype attribute on the <form> element.

<form action="/" method="post" enctype="multipart/form-data">
  <input type="text" name="description" value="some text" />
  <input type="file" name="myFile" />
  <button type="submit">Submit</button>
</form>

The request looks something like this (less interesting headers are omitted here):

POST /foo HTTP/1.1
Content-Length: 68137
Content-Type: multipart/form-data; boundary=---------------------------974767299852498929531610575

-----------------------------974767299852498929531610575
Content-Disposition: form-data; name="description"

some text
-----------------------------974767299852498929531610575
Content-Disposition: form-data; name="myFile"; filename="foo.txt"
Content-Type: text/plain

(content of the uploaded file foo.txt)
-----------------------------974767299852498929531610575--

Specifications

Specification
HTTP Semantics
# status.206
HTTP Semantics
# field.content-type

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
Content-Type
Yes
12
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Type