The new version of Burp employs heuristic rules to recognize most types of content commonly used in web applications. Information about response MIME types is used in various ways, for example:
Display filters in various locations allow you to show or hide different MIME types.
The Spider uses MIME type information to perform tailored content parsing.
You can define Proxy interception rules based on MIME type.
Vulnerability analysis performs different checks and actions based on a response's MIME type.