Updated: March 07, 2025

.MHTML File Extension

There is only one filetype that uses .MHTML file extension and it is MIME HTML File.

MIME HTML File

File category:	Web Files
Developer:	N/A
Open with:	Google Chrome (+5 more)
Platforms:	Windows, macOS, Linux, iOS, Android, ChromeOS, iPadOS

An MHTML file is a web page archive that stores all the content of a webpage in a single file. Unlike regular HTML files, MHTML captures not just the webpage code but also linked resources such as images, CSS stylesheets, JavaScript, audio files, and other elements that make up the complete webpage.

MHTML stands for "MIME Encapsulation of Aggregate HTML Documents" or simply "MIME HTML". This name reflects how the format encapsulates HTML content and its associated resources using MIME encoding standards.

MHTML was formally defined in RFC 2557, which established the specifications for this format. The format follows encoding principles similar to those outlined in message/rfc822, which relates to plain text email specifications.

How are MHTML files used?

MHTML files serve several purposes:

Web archiving: Web developers use MHTML to save the current state of a webpage for archival purposes.
Offline viewing: Users can save complete webpages for viewing when not connected to the internet.
Troubleshooting: Microsoft Windows uses the MHTML format to record scenarios of problems that occur during application usage.

The format is particularly useful because it preserves the entire webpage experience in a single file, making it easy to store and transfer.

How to Open .MHTML as MIME HTML File

Several applications can open MHTML files:

Web browsers:

Google Chrome
Microsoft Edge
Mozilla Firefox (with the Mozilla Archive Format plugin)

Other applications:

Microsoft Word/Office 365
Kingsoft Writer
WizHtmlEditor
Terra Informatics BlockNote.Net

Mobile devices with compatible browsers on Android and iOS can also open MHTML files.

How to create MHTML files

Creating MHTML files is straightforward in most modern browsers. For example, in Google Chrome:

Windows: Select More tools → Save page as... and choose Webpage, Single File
macOS: Select File → Save Page As... and choose Webpage, Single File

Additional Notes About MHTML

It's worth noting that MHTML files can potentially be used by cybercriminals to distribute malware. Always verify the source of any MHTML file before opening it to ensure it comes from a trusted source.

MHTML files may sometimes be saved with the alternative .MHT extension, though .MHTML is more common. They can also be renamed to .EML and opened as email files in compatible email clients.

The MHTML format encodes webpage content according to specifications defined in RFC 2557. It uses content headers like Content-Location to resolve URI references to resources contained within the file. This allows all linked components to be properly organized within a single archive while maintaining their relationships to the main HTML document.