ContentTypeHeader

Content-Type header

The Content-Type header is an HTTP header used to indicate the media type of the resource or payload associated with the message. In HTTP requests, it describes the format of the request body, such as JSON, form data, or binary uploads. In HTTP responses, it conveys the format of the response body so that clients can correctly interpret and render the content.

Content-Type uses MIME (or media) types defined by standards and registered with IANA. The header value can include parameters, such as a character encoding, for example: Content-Type: text/html; charset=utf-8. The charset parameter specifies how textual data should be interpreted by the client.

Common values include text/html, text/plain, application/json, application/xml, application/javascript, image/png, and video/mp4. The header is not required for all responses, but it is essential whenever a body is present because it informs the recipient how to handle the payload.

The Content-Type header is separate from the Accept header. While Content-Type tells the server or client what the body is, Accept communicates the formats the client can handle. Servers should set Content-Type to reflect the actual content delivered, and clients should verify it before processing the body to avoid misinterpretation or security issues.

In practice, Content-Type plays a central role in content negotiation, data parsing, and proper rendering across web applications, APIs, and services.