mht

MHT, in the most common usage, refers to MIME HTML, a web archive format used to save a complete web page as a single file. The standard extension is .mht or .mhtml. An MHT file encapsulates the HTML document and its associated resources—such as images, CSS, and scripts—into one MIME-encoded container, enabling offline viewing of the page without separate resource files.

Technical details include the use of the MIME type multipart/related. The top-level part contains the HTML, while referenced resources are included as additional parts, often encoded in base64. The HTML document typically refers to these embedded parts via content identifiers, allowing a self-contained page that can be opened later by compatible software.

History and usage notes indicate that MHT was popularized by Microsoft’s Internet Explorer in the 1990s and 2000s as a convenient way to preserve pages for later reference or offline access. Over time, browser support for native MHT handling has varied and diminished in many modern browsers. Some browsers offer optional or legacy support, while others require third-party plugins or enablement flags. As a result, saving pages as MHTML has become less common in mainstream browsing, with alternatives such as standard HTML with resource folders or PDF/web archive formats serving similar purposes.

Limitations and security considerations include potential risks from embedded scripts or malicious resources within an MHT file, as with any executable web content. Opening MHT files from untrusted sources can expose a system to security threats, and compatibility issues may arise when sharing files across different browsers and platforms.

See also: Web archives, Web page saving, Web Archive formats.