MHTML

MHTML stands for MIME HTML. It is used to bind resources which are typically represented by external links, such as image and sound files, together with HTML code into a single file. The content of an MHTML file is encoded as if it were an HTML email message, using the MIME type multipart/related. The first part is the HTML file, encoded normally; subsequent parts are additional resources, identified by their original URLs.

This format is sometimes referred to as MHT, after the suffix .mht given to such files by default when created by Microsoft Word, Internet Explorer or Opera. MHTML is a proposed standard, circulated in a revised edition in 1999 as RFC 2557.

Web browser support

Many browsers do not support this format, and the process for saving a web page along with its resources as an MHTML file is not standardized across those browsers that do. Due to this, a web page saved as an MHTML file using one browser may render differently on another.

Internet Explorer

The .mht format was introduced in 1999 with Internet Explorer 5.^[1] Saving in this format allows users to save a web page and its resources as a single MHTML file called a "Web Archive", where all images and linked files will be saved as a single entity. It may, however, be unable to save certain complex web pages correctly, especially those containing scripts.

Opera

Support for saving a web page with its resources as an MHTML file was made available in the Opera 9.0 web browser since the weekly build 8265 (released on March 10, 2006). In Opera 9.50 the default saving format for "Save as" function is MHTML. In Opera 9.50 it is possible to save web pages in following formats: 1) only with HTML, 2) HTML with pictures saved in separate folders 3) in TXT format and 4) with MHTML format.

Firefox

The web browser Mozilla Firefox, as of version 3.0.1, does not include direct support for saving or opening web pages as MHTML files. Though there is already source code available for viewing MHTML files within the Thunderbird project, this is filed as unsolved bug 18764 within the Firefox project since 1999.

There is an extension which adds MHTML support: UnMHT. This works in all versions of Firefox from 1.0 to the current one (as of 3.0.1). It is available under the MPL 1.1/GPL 2.0/LGPL 2.1 licence. The current version (v4.7.4) can write and open MHT files. It includes English and German locales. MHT files exported from MS Office (e.g. PowerPoint) are not supported.

For Firefox 1.5, this functionality can be obtained on Windows and Linux operating systems by installing a freely available third-party XPI file from Mozilla Archive Format extension, though the .mht files it generates are not fully compatible with Microsoft's products.^[2]

Safari

As of version 3.1.1 (released 2008-05-28), Apple Inc.'s Safari web browser does not support the MHTML format. Instead, it saves web pages in the webarchive format, which were directory bundles pre-3.0, but are now single file outputs.

There is a UnMHT port for Safari available^[3] based on SIMBL^[4] and GreaseKit.^[5]

Konqueror

As of version 3.5.7 (released 2007-05-02), KDE's Konqueror web browser does not support MHTML files. However, it does include a feature for saving web pages as single files ("web archives", file extension .war) which are actually gzipped tarballs.

ACCESS NetFront

NetFront 3.4 (on devices such as the Sony Ericsson K850) can view MHTML files, and also save open pages as mhtml (created with filename suffix .mhtml).

Editing support

All versions of Microsoft Word since Word 2002 can open and save MHTML documents.^[6][7] A converter is available from Microsoft to enable Word 2000 to open,^[8] and an add-on to allow it to save,^[9] MHTML files.

MHTML is also supported by Microsoft Word Viewer 2003, Microsoft Office Access 2003, Excel 2003, OneNote 2003, and PowerPoint 2003.^[10][11] Surprisingly, current versions of Microsoft's mainstream HTML editor products, such as Microsoft FrontPage and Microsoft Expression Web are unable to understand and parse MHTML format. They can only be forced to open MHTML files and display their contents as simple text.^[12][13][14] Microsoft SharePoint Designer 2007 has been reported to handle MHT files correctly.

On the Linux platform a utility called kmhtConvert is available to convert MHTML files to the KDE Web Archive format.^[15]

See also

• An alternative for attaching resources to an HTML document is the Data: URI scheme defined in IETF standard RFC 2397.

References

1. ^ New Features in Internet Explorer 5
2. ^ Feature Request: Support MS Web Archive Files
3. ^ UnMHT for Opera/Safari
4. ^ SIMBL
5. ^ greasekit - Google Code
6. ^ File formats Word can open and save without converters
7. ^ Saving a Microsoft Office Word 2003 document in a file format that cannot support specific features
8. ^ Microsoft Word Web Archive Converter for Word 2000
9. ^ Office 2000 Web Archive Add-on Available
10. ^ Microsoft Office Word Viewer 2003 Download Page, Overview section.
11. ^ About single file Web pages
12. ^ Microsoft Office FrontPage 2003, Microsoft Corporation
13. ^ Microsoft Office Sharepoint Designer, Microsoft Corporation. A fully-functional trial version is available from Microsoft web site.
14. ^ Microsoft Expression Web, Microsoft Corporation. A fully-functional trial version is available from Microsoft web site.
15. ^ Linux utility to convert mhtml files to KDE Web Archive files

External links

• MHTML standard explained
• MHT-rip - A program to view MHTML files on Linux
• RFC 2557 (1999) — MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)
• RFC 2110 (1997, Obsolete) — MIME E-mail Encapsulation of Aggregate Documents, such as HTML (MHTML)