The MHT file type is primarily associated with ‘MHTML Document’ by Microsoft Corporation. Archived Web Page. When you save a Web page as a Web archive in Internet Explorer, the Web page saves this information in Multipurpose Internet Mail Extension HTML (MHTML) format with a .MHT file extension. All relative links in the Web page are remapped and the embedded content is included in the .MHT file. The absolute references or hyperlinks on the Web page remain unchanged and the .MHT file is viewed using Internet Explorer. Note: This file type can become infected and should be carefully scanned if someone sends you a file with this extension.