File extension: .mht, .mhtml Developed by: W3C & WHATWG Type of format: Markup language MIME: application/x- mimearchive MHTML, short for MIME Encapsulation of Aggregate HTML Documents, is a web page archive format used to combine in a single document the HTML code and its companion resources that are otherwise represented by external links (such as images, Flash animations, Java applets, and audio files).