Associate MHT files with Firefox

Mozilla Firefox is a powerful browser. It offers many kinds of customizations and features. But like Opera and Internet Explorer, it does not offer native support for Web Archive files (also known as MHT files). In Opera or Internet Explorer you can save the entire page, including the HTML, Javascript and any images etc into a single Web Archive files. But Mozilla Firefox does not offer native support for MHT files.

But owing to the highly customizable nature of Firefox, you can add MHT functionality to Firefox in no time. What you need to do is download an add-on called unMHT ( and install it in Firefox. This add-on will add the Save as MHT and Save all tabs as MHT in the File menu of Firefox. Now you can save any page or all pages open in tabs of Firefox to a web archive MHT file.

The unMHT add-on working in Mozilla Firefox

The problem with unMHT Firefox add-on is that, by default, it allows you to save files only. If you double-click on any of the saved MHT files, it opens in Internet Explorer. Its no fun to use Firefox to save the MHT files and then to have to open them using Internet Explorer. You can associate MHT files with Firefox so when you double-click on MHT files, they open in Firefox instead of Internet Explorer. To associate MHT files with Firefox follow these steps :

  1. Make Firefox your default browser (Its pointless to associate only MHT files to Firefox). To make Firefox your default browser, Open Tools → Options → Advanced in Firefox and click on Check Now. When asked choose Yes.
  2. Right-click on an MHT file and select Properties. (If you do not have an MHT file, you can create using either Internet Explorer or Firefox web browser. In Firefox, just open a webpage and choose File → Save as MHT.)

    Right-click on a file and Properties

  3. In the Properties window, click on the Change button.

    Click on the Change button in Properties window

  4. In Windows Vista/7, click on the Browse button and browse to firefox.exe. In Windows XP, you can browse the firefox.exe directly. The firefox.exe file is typically located in C:Program FilesMozilla Firefox folder. Select the Firefox.exe and click OK.

    Browse for the Firefox.exe

  5. Click on the OK button on all the open windows to save the changes.
  6. Enjoy viewing MHT files in Mozilla Firefox.


  1. The link you have for the unMHT addon returns a “Page Not Found”. It may be that the addon is not available anymore. That’s too bad ‘cuz it’s what I need to “view in web browser” my email in Firefox instead of IE.

  2. Great to know, and ALMOST what I was looking for, but any ideas how can I do the same on my Android device with Firefox for Android? Presently, it tries to open them with Adobe Acrobat, which fails. (Android is a terrible OS).

    Oh! Or could I just do that on a Windows machine, with an MHT on my SD card, and it would carry over?

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