MHTML is an 8-bit MIME-encoded webpage file. MHTML file stores webpage HTML document along with linked resources such as images or audio files. MHTML is similar to the MHT extension; MHTML files are typically created by Microsoft Word.

MHTML files aggregate HTML document and related external URL resources into single document. Depending on the web browser used, some MHTML documents may be rendered differently. Some MHTML documents require that additional plugins be installed in order to correctly render the contents.