Content-Type header

Syntax

Content-Type: <media-type>

For example:

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

Directives

<media-type>

The media type of the resource or data. May contain the following parameters:

• charset: Indicates the character encoding standard used. The value is case insensitive but lowercase is preferred.
• boundary: For multipart entities, the boundary parameter is required. It is used to demarcate the boundaries of the multiple parts of the message. The value consists of 1 to 70 characters (not ending with white space) known to be robust in the context of different systems (e.g., email gateways). Often, the header boundary is prepended by two dashes in the request body, and the final boundary has two dashes appended at the end.

Examples

Serving assets with correct content type

In the following two example responses, JavaScript and CSS assets are served using text/javascript for JavaScript and text/css for CSS. The correct content type for these resources helps the browser handle them more securely and with better performance. See Properly configuring server MIME types for more information.

HTTP/1.1 200
content-encoding: br
content-type: text/javascript; charset=utf-8
vary: Accept-Encoding
date: Fri, 21 Jun 2024 14:02:25 GMT
content-length: 2978

const videoPlayer=document.getElementById...

HTTP/3 200
server: nginx
date: Wed, 24 Jul 2024 16:53:02 GMT
content-type: text/css
vary: Accept-Encoding
content-encoding: br

.super-container{clear:both;max-width:100%}...

Content-Type in multipart 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="/foo" method="post" enctype="multipart/form-data">
  <input type="text" name="description" value="Description input value" />
  <input type="file" name="myFile" />
  <button type="submit">Submit</button>
</form>

The request looks something like the following example with some headers omitted for brevity. In the request, a boundary of ExampleBoundaryString is used for illustration, but in practice, a browser would create a string more like this ---------------------------1003363413119651595289485765.

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

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

Description input value
--ExampleBoundaryString
Content-Disposition: form-data; name="myFile"; filename="foo.txt"
Content-Type: text/plain

[content of the file foo.txt chosen by the user]
--ExampleBoundaryString--

Content-Type in URL-encoded form submission

When forms don't involve file uploads and are using simpler fields, URL-encoded forms may be more convenient where the form data is included in the request body:

<form action="/submit" method="post">
  <label for="comment">Comment:</label>
  <input type="text" id="comment" name="comment" value="Hello!" />
  <button type="submit">Submit</button>
</form>

POST /submit HTTP/1.1
Host: example.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 15

comment=Hello!

Content-Type in a REST API using JSON

Many REST APIs use application/json as a content type which is convenient for machine-to-machine communication or programmatic interaction. The following example shows a 201 Created response showing the result of a successful request:

HTTP/1.1 201 Created
Content-Type: application/json

{
  "message": "New user created",
  "user": {
    "id": 123,
    "firstName": "Paul",
    "lastName": "Klee",
    "email": "p.klee@example.com"
  }
}

Specifications

Browser compatibility

See also

• Accept, Accept-Encoding, Accept-Language headers
• Vary
• Content-Encoding
• Content-Disposition
• 206 Partial Content
• X-Content-Type-Options