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How To Change User Agent String

The question of What’s that user agent string used for? should has been duly answered in the previous post. The next question is about How to change or spoof user agent string?

Why there is a need to change or spoof user agent string?

Well, this question should have been answered in the previous post too. In short, changing or spoofing user agent string is needed when online security is a concern or to bypass web services access restriction for certain type of web browser.

For example, Adobe Reader download site will display different download page according to the web browser that visiting the site, limit or auto pick up Adobe Reader version for the OS type in the user agent string, force Adobe Updater to manage Adobe Reader download progress. So, by changing the user agent string, one can directly download any Adobe Reader version of any platforms or languages with Internet Explorer or Mozilla Firefox, without using the Adobe Updater or Opera web browser!

How to change User Agent String of Internet Explorer?

The structure of Internet Explorer user agent string.
The template of user agent string used by Microsoft Internet Explorer.

For Internet Explorer 6 SP2 on Windows 2000 and IE7 For Windows XP, open up Windows Registry Editor to locate this Registry key:
HKLM\Software\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent

and change the Version string value to Opera/9.21. If the Version key is not there, create the Version key of REG_SZ type (string type) with the spoofing user agent string value (i.e. Opera/9.21)!

For IE7 in Windows Vista, you can just copy and paste these Reg commands in the Vista Command Prompt and press ENTER:

To add the Version key with a spoofing user agent string value:
%windir%\System32\cmd.exe /k %windir%\System32\reg.exe ADD "HKLM\Software\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent" /v Version /d "Opera/9.2.1" /f

To delete the Version key and revert back to original user agent string value:
%windir%\System32\cmd.exe /k %windir%\System32\reg.exe DELETE "HKLM\Software\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent" /v Version /f

How to change User Agent String of Opera 9.21 web browser?
  1. Type opera:config in the Opera address bar and press ENTER,
  2. Type Spoof UserAgent ID in the text-box next to Show All
  3. Change the Spoof User Agent ID to any one of these supported user agent string:
    1 = Opera (default user agent string of Opera)
    2 = Mozilla
    3 = Internet Explorer
    4 = Mozilla, Opera not mentioned
    5 = Internet Explorer, Opera not mentioned
  4. Save the change made before exit and restart Opera 9.21

How to change User Agent String of Mozilla Firefox?
  1. Type about:config in the Mozilla Firefox address bar and press ENTER,
  2. Type general.useragent.extra.firefox in the Filter bar,
  3. Double-click on the returned Firefox setting, where you can change or spoof a user agent string to overwrite the default “Firefox/”!

Custom Search

  1. Rundll32 Programmatically Delete IE7 Browsing History – Walker News 07-07-07@23:34

    […] Mozilla Firefox, you can set it to clear all browsing history upon closing the last instance Firefox […]

  2. Walker 19-07-07@11:39


    For Firefox, you should change the Firefox user agent string via


  3. How To Download Adobe Reader Full Setup File For Different OS – Walker News 29-06-08@17:36

    […] default, the download page detects user agent string and present Adobe Reader download link that matches with the client’s OS. The Adobe Download […]

  4. anthony 07-08-08@05:05

    “# Type opera:config in the Opera address bar and press ENTER,

    # Type Spoof UserAgent ID in the text-box next to Show All

    # Change the Spoof User Agent ID to any one of these supported user agent string: ”

    It does not work. :-(

  5. Hwo To Change Firefox User Agent String? 27-09-09@21:39

    […] particular web browsers? The answer is certainly YES, according to Johne. (I was wrong in an earlier post talking about the same topic :-( Step to change Firefox user agent string FYI, these steps are […]

  6. wap-tek 24-04-10@11:56

    after you try to spoof opera’s user agent string,
    test it on http://www.danasoft.com/

    opera ALWAYS admits your using opera and
    your operating system version
    so no ,, NO! it does not ” Mask as ” anything

    using user.js is NOT well explained and i bet it fails as well

    just give up and drink the !#%^* flavoraid!

  7. just some guy 27-05-10@00:25

    Using Opera I selected Tools -> Quick Preferences -> Identify as ->
    (Opera, Mozilla, and IE are the options), and danasoft reported back whatever I put in.

  8. treaz 29-07-10@18:22

    really helpful… I’m glad it popped up as the first result in Google.


  9. john 11-06-15@13:32

    I’ve been using Opera for over a decade. It used to be great. When I first started using Metropcs, the only way I could connect my notebook to the mobile hotspot was by changing Opera’s useragent string. Used to change using opera:config like listed above. But those who say it doesn’t work are RIGHT because about 2 years ago it quit working. I can’t use Opera with my Metro hotspot because Metro shuts it off recognizing it as a Windows Opera browser not the linux version I used to use. I have tried every version of Opera from 12.02 up and NONE of them allow me to change the Useragent string. It SAYS it does but it doesn’t work, and when I go back to opera:config useragent it is back to default every time. Also when I go to useragentstring.com it is the same old setting to. Every mobile, mini, android etc version of Opera I can find I have tried over the last 2 years. Not one has changed. It used to, because I had bookmarks for opera:config and useragentstring.com which worked every time as should. Not my pc either because I have tried 3 different computers and none work. I know it is Opera too because until recently I could use Firefox. But Metropcs must now be f’ing with the useragentstring ID’s (which makes it now impossible to tell if I got a ‘right working’ Opera because for some reason the last week I have not been able to use my mobile hotspot AT ALL, PERIOD, NO MATTER WHAT BROWSER I TRY but I found out by accident if I run HotSpot Shield it will connect with I.E. but not Firefox anymore and still not Opera.
    Any ideas how to try to make Opera KEEP the useragentstring that it’s told to keep?

  10. john 11-06-15@13:55

    why won’t opera change and save useragent?

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