I am working on a production issue which only occurs in IE10 and not in chrome/Firefox. If I change the IE10's user-agent (F12) to Mozilla Firefox it works.

I need to debug the app. layer to find the issue, but till that can I suggest my client to modify user-agent.

The client due to security & other org policy do not and cannot use/install any other browser other than IE10.

Note: The errors are not client specific, the service which client code calls is failing.

What are the implications, in general of changing the user-agent of a browser (leaving aside any business logic conditional to the browser)?

  • None at all. I don't believe any browser behaves differently based on how you set its User-Agent string. – reinierpost May 11 '15 at 8:03

When you change the user-agent in a browser, changes the way web servers recognize you, not the way the browser works.


Changing the user agent will not have any impact on performance or security.

I wonder why doing so changes the behavior of the client anyway. It is possible that, apart from sending the user agent in the HTTP request, IE tries to behave differently when executing JavaScript or parsing HTML (i.e. maybe after you have changed the user agent it wont get in the <!--[if IE]> code chunks?). If this happens then the problem is that different browsers are executing/parsing different code.

  • maybe I missed to indicate, but the error is not at the client side, the service URL that client calls is failing. The URL even fails when directly hitting it in browser's address bar(with an active session), but only in IE. – akjain May 11 '15 at 8:43
  • @akjain: yeah, you can definitely change (i.e. redirect, deny...) the request on the server side depending on the user agent. Before IE 10, user agent mayor versions had one digit. Maybe the server is getting the first digit (1) and perhaps it is not even responding to such "old" versions of IE. The problem may be hard to find/solve, but the answer to your question is clear anyway: it wont have implications on security/performance. ;-) – Peque May 11 '15 at 8:54
  • @akjain: have you tried with IE 9? And IE 11? (if it exists, I don't know xD) – Peque May 11 '15 at 8:57
  • Yes even with IE9, same issue. – akjain May 11 '15 at 9:16
  • @akjain: well, you can tell your client to change the user agent while you try to find the problem. Remember that yeah, your server can change its behavior depending on the user agent (if that's what it has been told to do, of course). Good luck. – Peque May 11 '15 at 9:48

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