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Effectiveness of User agent (useragent)

  • 13 replies
  • 2 have this problem
  • 268 views
  • Last reply by cor-el

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Hello to everybody :o)

several websites, i.e. YouTube, Facebook and Google, detect the actual version of Firefox despite the fact I set a different version number (more recent) by means of the "User Agent Switcher" plugin.

So my question is twofold:

1) how can I change the "fingerprint" of my Firefox effectively, in order to make *any* website recognize the version number which I set (and not the real one)?

2) how those websites do detect the ACTUAL identity of a given browser, despite the changes to the User Agent string that one may have made by means of a switcher?

Thank you in advance to all you folks!

All Replies (13)

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Why are you wanting to do this? I guess I'm just trying to figure out your motive so we can address that.

Also, are you really using Windows 2000? If not, please update to Firefox 31. Also, update your flash, it's very out of date.

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Good morning Tyler, and thank you for your answer.

You saw Windows 2000 because I was writing from a computer (not mine) whose operating system cannot be changed due to logistic issues and compatibility problems with one of the applications installed (I won't go into more details since it's not my PC). For the same reason (compatibility with Win2000) Firefox could not be updated beyond a certain version.

My purpose is to investigate the usage of "User Agent sniffing" by a few websites. While in some cases the contents of certain web pages is changed with the genuine purpose of ensuring functional compatibility with a given browser, in other cases I suspect that certain functions of the web site/page are intentionally inhibited for browser versions "older than XYZ", although the browser would be perfectly able to support them, for the sole purpose of forcing (exasperating?...) the site visitor to change his/her browser to another version. In other words, I suspect that there are websites which prevent the visitor from using certain functions if a given browser version is detected, not due to real compatibility needs, but only to coerce the visitor to change his/her browser. I guess there is nothing bad in doing some research on my own, isn't it?... :o)

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Sorry cor-el, my original question had nothing to do with Windows 2000, I guess that you were misleaded by an incidental question about the O.S. of the PC from where I was writing. Thank you anyway.

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I wrote that so you can install a more recent Firefox version on the computer that runs Windows 2000.

There is more than one way to detect the current Firefox version. One is the navigator.userAgent property. Another is the user agent as send via the HTTP request headers. It is also possible to check for supported features in the browser via JavaScript and the latter can't be affected.

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Hello cor-el, sorry for the delay in answering you, I was away on (much sought after) holiday! :o) It seems that there is no fast-and-simple way to change the fingerprint so Firefox would effectively look like a more recent version...

Just one last question, if you allow me.

I am assuming that my current version of Firefox actually supports all the features needed (I am quite confident in that respect) so your statement "It is also possible to check for supported features in the browser via JavaScript" would not really pose an obstacle. I'm thinking of the other thing you wrote: "Another is the user agent as send via the HTTP request headers".

Is there any feasible way to change *that*?

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It's probably possible that 12 doesn't support all the latest features, check out http://html5test.com/results/desktop.html to see just what HTML5 features it doesn't support. (Firefox 30 scores 467, Firefox 12 scores 357). As the internet continues to advance, your computer will be left further and further behind, and no spoofing of user agents is going to fix that.

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With Firefox, you now need the additional extension "User-agent JS Fixer" to add the fake string to the request header.

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Thank you for the hint finitarry! (and excuse me for the delay in answering... lately, I'm travelling a lot due to my job :-( )

Just one question: in order for my browser to effectively behave as another version of the same browser, in addition to that "User-agent JS Fixer" do I need to install any other extension?...

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To have a really convincing fake, you should fill in all the blanks in the entry inside User-agent Switcher, except for the vendor info. The .xml file you can get for that extension does not fill in all that data, and it is important if you want a fake to be really convincing. Some sites use javascript to do more probing of the browser. You can get an idea of what that should be from setting up a new user agent using the editor.

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finitarry said

To have a really convincing fake, you should fill in all the blanks in the entry inside User-agent Switcher, except for the vendor info. The .xml file you can get for that extension does not fill in all that data, and it is important if you want a fake to be really convincing. Some sites use javascript to do more probing of the browser. You can get an idea of what that should be from setting up a new user agent using the editor.

Hello finitarry! Again, I apologize for answering so late: my employer keeps shipping me around, I'm starting to feel like a piece of luggage (sometimes I think I must have an airline label pasted somewhere), and under these conditions it's so difficult to handle my (very little) spare time satisfactorily... About the User Agent switcher, I assume that you were talking about this program:

https://addons.mozilla.org/it/firefox/addon/user-agent-switcher/?src=ss

For the abovesaid reasons (almost no spare time) I could not install and try it yet, but I read several opinions by the folks who used it, and the two most common complaints seems to be: 1) that program is anything but user-friendly (excessively complex to set up), and 2) it does not retain the settings between two sessions. I'm wondering whether you do know of any user agent switcher which does not need a degree in computer science, which I can't take ;o) . If you don't, could you please tell be the basic information and tips about setting up a "convincing" fake? Like the location of that .XML file you mentioned, and what to fill in what fields...

To Tyler Downer, and any of you folks who may be interested in my little investigation: I discovered that one social network has recently introduced a feature which disables the "paste" function ONLY in certain types of posts, while allowing it to work in other areas of the page, if the browser is older than XYZ. This is a fitting example of what I meant in my second post in this thread: the copy/paste function is a very basic feature in any OS and browser, the browser is perfectly able to support it (of course!), but they intentionally prevent you from using it with the sole purpose of exasperating you to the point that you decide to change your software, actually at their will. I feel it's like being manipulated, and I find this behaviour very irritating.

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You can download a list of fake user-agents in an .xml file and it can be used with User Agent Switcher. The only problem is that it has filled in only the user-agent string that is in the browser's request header, and a convincing fake needs more than that. You would see what I meant if you installed that extension. If you click the button, choose "Edit User Agents", click "New", then "New User Agent", you will see that some information is filled out for you. That is the type of information that should be in the fake.

The fake user-agent is not carried through from one session to the next, but it is easy to find it and click it again.

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If web servers check for feature support in the browser instead of using the user agent that it won't help to spoof the user agent. There is usually no need to change the user agent unless you need to visit websites that only work with older Firefox versions and in such a case it might still not work. A lot of servers send files for different browsers and Operating Systems and might not work properly.