Content-TypeContent-Type is a term used in Multipurpose Internet Mail Extensions (MIME). It is a text protocol header that tells an application such as a browser what type of data is about to be sent. Once the application knows what type of data is coming, it determines whether or not it can handle the data, or if it has to call another program to help. For example, most browsers know how to handle HTML data; however, if 3-D information is presented, the browser may need to call on a helper application to format and display the data.