How To Make Firefox Display Mobile Versions Of Websites On A PC

It is easy to make the desktop version of Firefox request the mobile version of websites using the Go-Mobile extension.

Many websites offer a mobile friendly version if you are browsing from a phone – they are less graphically intensive and may make use of excerpts to ensure that they are quicker to load and do not use up as much of your precious data allowance.

There may be several reasons why you prefer to visit the mobile version of sites like Gmail, Facebook and Google etc – even though you are using the desktop version of Firefox:

  • 1. If you have a dial up internet connection, or very slow broadband (e.g. 2G/3G) then browsing mobile versions of websites can significantly speed up web browsing.
  • 2. You may prefer the streamlined look of some mobile sites which offer a simpler interface with less clutter and flash videos etc.
  • 3. Some ISPs offer higher/unlimited data plans for mobile devices but not for PCs – imitating a mobile device when browsing on a PC may allow you to take advantage of those higher mobile limits.
  • 4. Web developers may want a quick way to check how their site functions from a mobile perspective (although the HTML rendering will not be the same as a genuine mobile device – for better HTML results, Google offer GoMo as a free online check of any website).

Go-Mobile – a simple new extension to tell websites that your version of Firefox is actually Firefox on an Android phone. It adds a ‘phone’ icon to the Firefox Add-on bar – click the icon to toggle the feature on or off.

Download the extension from Mozilla Add-ons here. After installation there is nothing to configure – you should see the new phone icon appear in the add-on bar. If the add-on bar is not displayed you can make it appear via Firefox menu \ View \ Toolbars \ Add-on bar or use the CTRL + / hotkey.

Click the phone icon to turn ‘mobile mode’ On (as shown below) or Off for future pages – if you want to see the change applied to the current page you must refresh it.


Mobile mode On

Note that when Firefox restarts, the icon is automatically reset to ‘desktop’ mode.

How It Works – The extension works by changing the value of the user agent which identifies the web browser. Whenever a browser requests a page, it sends the user agent to the web server – if the user agent is of a mobile browser, the web server will return that version of the site (if there is one).

The add-on creates a new preference in Firefox about:config called general.useragent.override which, as the name suggests, overrides the standard desktop Firefox user agent.

When you toggle phone mode On, the value of this preference is set to Mozilla/ (Android; Mobile;) Gecko/ Firefox/ so that web servers think you are using Firefox on an Android phone – when toggled Off, it changes the value of the preference to blank (i.e. no override so the standard desktop Firefox user agent is used).

Manual Alternative – Experienced users will realize that you could just add the new general.useragent.override preference yourself (as a new String) in about:config and set the value as required but of course the benefit of the extension is that it offers a single click process to switch immediately between each mode.


Go-Mobile is a simple extension to make Firefox request the mobile version of a website and it is easy to switch the function on or off.

There are other Firefox add-ons which let you switch the user agent to one of many (e.g. to another desktop browser, not just mobile) but, the more functionality they have, the more likely they may cause problems.

If you only need the ability to quickly view mobile versions of some websites, Go-Mobile does this basic job very well.

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4 Responses to: "How To Make Firefox Display Mobile Versions Of Websites On A PC"

  1. sfdude says:

    Sounds like a very good idea!.

    But…. the addons MOZ site, says
    that “Go Mobile” is not compatible
    with my
    FF 16.02 browser, (under XP Pro 32 bit).
    and refuses to install it.

    What is the minimum FF version # it requires?


    • Roy says:

      @sfdude – no idea on the minimum as I don’t keep older versions of FF but it’s ok on the current FF 18.0.2 on XP.

      Unless you have a really good reason, you should update to the latest FF18 anyway – there have been loads of security updates (as well as feature changes) since 16…

  2. Ken James Gertner says:

    This sounds like a very useful tool, thanks for the heads up.

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