MHTML

MHTML
Filename extension .mht, .mhtml
Internet media type multipart/related application/x-mimearchive
Type of format Markup language
Extended from HTML
Standard RFC 2557 (proposed 1999)

MHTML, short for MIME Encapsulation of Aggregate HTML Documents, is a web page archive format used to combine in a single document the HTML code and its companion resources that are otherwise represented by external links (such as images, Flash animations, Java applets, and audio files). The content of an MHTML file is encoded as if it were an HTML e-mail message, using the MIME type multipart/related.

In practical terms, MHTML allows multiple elements of a web page—including images and other media that would typically be saved in a folder as separate files alongside an HTML document—to be saved altogether as a single MHTML file. It does so by expanding upon methods originally developed to enrich email content.[1]

The first part of the file is an e-mail header. The second part is normally encoded HTML. Subsequent parts are additional resources identified by their original URLs and encoded in base64. 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 open standard, circulated in a revised edition in 1999 as RFC 2557.

The .mhtml (Web archive) and .eml (e-mail file) file extensions are interchangeable (the files can be renamed). The first can be sent by e-mail (and displayed by the email client if the html code is basic enough) and an e-mail message can be saved to an OS file and renamed to a Web archive extension.

Browser support

Some browsers support the MHTML format, either directly or through third-party extensions, but the process for saving a web page along with its resources as an MHTML file is not standardized. Due to this, a web page saved as an MHTML file using one browser may render differently on another.

Internet Explorer

As of version 5.0, IE was the first browser to support reading and saving web pages and external resources to a single MHTML file.

Opera

Support for saving web pages as MHTML files was made available in the Opera 9.0 web browser.[2] From Opera 9.50 through the rest of the Presto-based Opera product line (currently at Opera 12.16 as of 19 July 2013), the default format for saving pages is MHTML. The initial release of the new Webkit/Blink-based Opera (Opera 15) did not support MHTML, but subsequent releases (Opera 16 onwards) do.

MHTML can be enabled by typing "opera://flags#save-page-as-mhtml" at the address bar.

Google Chrome

Creating MHTML files in Google Chrome (v25+) is supported by toggling the experimental "Save Page as MHTML" option by visiting the link "chrome://flags/#save-page-as-mhtml" in the Chrome browser.

Firefox

Mozilla Firefox does not support MHTML.[3] Until the advent of version 57 ("Firefox Quantum"), MHT files could be read and written by installing a browser extension, such as Mozilla Archive Format or UnMHT.

Safari

As of version 3.1.1 onwards, Apple Inc.'s Safari web browser still does not natively support the MHTML format. Instead, Safari supports the webarchive format, and the macOS version includes a print-to-PDF feature.

As with most other modern web browsers, support for MHTML files can be added to Safari via various third-party extensions.

Konqueror

As of version 3.5.7, KDE's Konqueror web browser does not support MHTML files. An extension project, mhtconv, can be used to allow saving and viewing of MHTML files.

ACCESS NetFront

NetFront 3.4 (on devices such as the Sony Ericsson K850) can view and save MHTML files.

Pale Moon

Pale Moon requires an extension to be installed to read and write MHT files. One extension is freely available, MozArchiver, a fork of Mozilla Archive Format extension.

GNOME Web

In recent versions of GNOME Web it is possible to save web pages as MHTML.

Vivaldi

Vivaldi supports both reading and writing MHTML files by toggling the "vivaldi://flags/#save-page-as-mhtml" option.

MHT viewers

There are commercial software products for viewing MHTML files and converting them to other formats, such as PDF and ePub. Some HTML editor programs can view and edit MHTML files.

MIME type

MIME type for MHTML is not well agreed upon. Used MIME types include:

  • multipart/related
  • application/x-mimearchive
  • message/rfc822

Other apps

Problem Steps Recorder

Problem Steps Recorder for Windows can save its output to MHT format.

Save to Google Drive extension

The "Save to Google Drive" extension for Google Chrome can save as MHTML as one of its outputs.

Microsoft OneNote

Microsoft OneNote, starting with OneNote 2010, emails individual pages as .mht files.

Evernote

Evernote for Windows can export notes as MHT format, as an alternative to HTML or its own native .enex format.

See also

References

  1. ↑ Amanda Holden. "Difference of HTML & MHTML". Archived from the original on 17 November 2017. Retrieved 17 November 2017.
  2. ↑ Santambrogio, Claudio (10 March 2006). "…and one more weekly!". Opera Software. Archived from the original on 15 January 2010. Retrieved 2009-05-15.
  3. ↑ "Bug 40873 - Save as rfc 2557 MHTML; complete webpage in one file".
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