Sisällöntyyppimerkintä

Sisällöntyyppimerkintä, known in English as Content-Type, is a standard HTTP header field that defines the media type of the resource being transmitted. It informs the recipient of the format of the data, allowing them to process it correctly. For example, when a web server sends an HTML document, the Content-Type header would be set to text/html. If it sends an image, it might be image/jpeg or image/png.

This header is crucial for the proper functioning of the web. Browsers rely on the Content-Type to know how to render the received data. If the Content-Type is incorrect or missing, a browser might display raw text instead of an image, or attempt to download a file instead of rendering it as a webpage. The Content-Type header follows the Media Type specification, which uses a type and subtype notation, such as text/plain, application/json, or video/mp4.

Beyond basic media types, the Content-Type header can also include parameters. A common parameter is charset, which specifies the character encoding of the text data, such as text/html; charset=utf-8. This ensures that characters are interpreted and displayed correctly across different languages and systems. In essence, the Content-Type header acts as a vital piece of metadata that facilitates smooth and accurate communication between clients and servers on the internet.